Make "print" and "compile print" support -OPT options

Make "print" and "compile print" support -OPT options

This patch adds support for "print -option optval --", etc.
Likewise for "compile print".

We'll get:

~~~~~~
(gdb) help print
Print value of expression EXP.
Usage: print [[OPTION]... --] [/FMT] [EXP]

Options:
  -address [on|off]
    Set printing of addresses.

  -array [on|off]
    Set pretty formatting of arrays.

  -array-indexes [on|off]
    Set printing of array indexes.

  -elements NUMBER|unlimited
    Set limit on string chars or array elements to print.
    "unlimited" causes there to be no limit.

  -max-depth NUMBER|unlimited
    Set maximum print depth for nested structures, unions and arrays.
    When structures, unions, or arrays are nested beyond this depth then they
    will be replaced with either '{...}' or '(...)' depending on the language.
    Use "unlimited" to print the complete structure.

  -null-stop [on|off]
    Set printing of char arrays to stop at first null char.

  -object [on|off]
    Set printing of C++ virtual function tables.

  -pretty [on|off]
    Set pretty formatting of structures.

  -repeats NUMBER|unlimited
    Set threshold for repeated print elements.
    "unlimited" causes all elements to be individually printed.

  -static-members [on|off]
    Set printing of C++ static members.

  -symbol [on|off]
    Set printing of symbol names when printing pointers.

  -union [on|off]
    Set printing of unions interior to structures.

  -vtbl [on|off]
    Set printing of C++ virtual function tables.

Note: because this command accepts arbitrary expressions, if you
specify any command option, you must use a double dash ("--")
to mark the end of option processing.  E.g.: "print -o -- myobj".
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I want to highlight the comment above about "--".

At first, I thought we could make the print command parse the options,
and if the option wasn't recognized, fallback to parsing as an
expression.  Then, if the user wanted to disambiguate, he'd use the
"--" option delimiter.  For example, if you had a variable called
"object" and you wanted to print its negative, you'd have to do:

  (gdb) print -- -object

After getting that working, I saw that gdb.pascal/floats.exp
regressed, in these tests:

 gdb_test "print -r" " = -1\\.2(499.*|5|500.*)"
 gdb_test "print -(r)" " = -1.2(499.*|5|500.*)"
 gdb_test "print -(r + s)" " = -3\\.4(499.*|5|500.*)"

It's the first one that I found most concerning.  It regressed because
"-r" is the abbreviation of "-raw".  I realized then that the behavior
change was a bit risker than I'd like, considering scripts, wrappers
around gdb, etc., and even user expectation.  So instead, I made the
print command _require_ the "--" options delimiter if you want to
specify any option.  So:

  (gdb) print -r

is parsed as an expression, and

  (gdb) print -r --

is parsed as an option.

I noticed that that's also what lldb's expr (the equivalent of print)
does to handle the same problem.

Going back the options themselves, note that:

 - you can shorten option names, as long as unambiguous.
 - For boolean options, 0/1 stand for off/on.
 - For boolean options, "true" is implied.

So these are all equivalent:

 (gdb) print -object on -static-members off -pretty on -- foo
 (gdb) print -object -static-members off -pretty -- foo
 (gdb) print -object -static-members 0 -pretty -- foo
 (gdb) print -o -st 0 -p -- foo

TAB completion is fully supported:

  (gdb) p -[TAB]
  -address         -elements        -pretty          -symbol
  -array           -null-stop       -repeats         -union
  -array-indexes   -object          -static-members  -vtbl

Note that the code is organized such that some of the options and the
"set/show" commands code is shared.  In particular, the "print"
options and the corresponding "set print" commands are defined with
the same structures.  The commands are installed with the
gdb::option::add_setshow_cmds_for_options function.

gdb/ChangeLog:
2019-06-13  Pedro Alves  <palves@redhat.com>

	* compile/compile.c: Include "cli/cli-option.h".
	(compile_print_value): Scope data pointer is now a
	value_print_options pointer; adjust.
	(compile_print_command): Process options.  Scope data pointer is
	now a value_print_options pointer; adjust.
	(_initialize_compile): Update "compile print"'s help to include
	supported options.  Install a completer for "compile print".
	* cp-valprint.c (show_vtblprint, show_objectprint)
	(show_static_field_print): Delete.
	(_initialize_cp_valprint): Don't install "set print
	static-members", "set print vtbl", "set print object" here.
	* printcmd.c: Include "cli/cli-option.h" and
	"common/gdb_optional.h".
	(print_command_parse_format): Rework to fill in a
	value_print_options instead of a format_data.
	(print_value): Change parameter type from format_data pointer to
	value_print_options reference.  Adjust.
	(print_command_1): Process options.  Adjust to pass down a
	value_print_options.
	(print_command_completer): New.
	(_initialize_printcmd): Install print_command_completer as
	handle_brkchars completer for the "print" command.  Update
	"print"'s help to include supported options.
	* valprint.c: Include "cli/cli-option.h".
	(show_vtblprint, show_objectprint, show_static_field_print): Moved
	here from cp-valprint.c.
	(boolean_option_def, uinteger_option_def)
	(value_print_option_defs, make_value_print_options_def_group):
	New.  Use gdb::option::add_setshow_cmds_for_options to install
	"set print elements", "set print null-stop", "set print repeats",
	"set print pretty", "set print union", "set print array", "set
	print address", "set print symbol", "set print array-indexes".
	* valprint.h: Include <string> and "cli/cli-option.h".
	(make_value_print_options_def_group): Declare.
	(print_value): Change parameter type from format_data pointer to
	value_print_options reference.
	(print_command_completer): Declare.

gdb/testsuite/ChangeLog:
2019-06-13  Pedro Alves  <palves@redhat.com>

	* gdb.base/options.exp: Build executable.
	(test-print): New procedure.
	(top level): Call it, once for "print" and another for "compile
	print".