Fix advance/until and multiple locations (PR gdb/26524)

Fix advance/until and multiple locations (PR gdb/26524)

If you do "advance LINESPEC", and LINESPEC expands to more than one
location, GDB just errors out:

   if (sals.size () != 1)
     error (_("Couldn't get information on specified line."));

For example, advancing to a line in an inlined function, inlined three
times:

 (gdb) b 21
 Breakpoint 1 at 0x55555555516f: advance.cc:21. (3 locations)
 (gdb) info breakpoints
 Num     Type           Disp Enb Address            What
 1       breakpoint     keep y   <MULTIPLE>
 1.1                         y   0x000055555555516f in inline_func at advance.cc:21
 1.2                         y   0x000055555555517e in inline_func at advance.cc:21
 1.3                         y   0x000055555555518d in inline_func at advance.cc:21
 (gdb) advance 21
 Couldn't get information on specified line.
 (gdb)

Similar issue with the "until" command, as it shares the
implementation with "advance".

Since, as the comment in gdb.base/advance.exp says, "advance <location>"
is really just syntactic sugar for "tbreak <location>;continue",
fix this by making GDB insert a breakpoint at all the resolved
locations.

A new testcase is included, which exercises both "advance" and
"until", in two different cases expanding to multiple locations:

  - inlined functions
  - C++ overloads

This also exercises the inline frames issue fixed by the previous
patch.

gdb/ChangeLog:

	PR gdb/26524
	* breakpoint.c (until_break_fsm) <location_breakpoint,
	caller_breakpoint>: Delete fields.
	<breakpoints>: New field.
	<until_break_fsm>: Adjust to save a breakpoint vector instead of
	two individual breakpoints.
	(until_break_fsm::should_stop): Loop over breakpoints in the
	breakpoint vector.
	(until_break_fsm::clean_up): Adjust to clear the breakpoints
	vector.
	(until_break_command): Handle location expanding into multiple
	sals.

gdb/testsuite/ChangeLog:

	PR gdb/26523
	PR gdb/26524
	* gdb.base/advance-until-multiple-locations.cc: New.
	* gdb.base/advance-until-multiple-locations.exp: New.