Fix gdb.ada/complete.exp's "complete break ada" test (PR gdb/22670)

Fix gdb.ada/complete.exp's "complete break ada" test (PR gdb/22670)

This patch fixes the regression covered by the test added by:

    commit 344420da6beac1e0b2f7964e7101f8dcdb509b0d
    Date: Thu Jan 4 03:30:37 2018 -0500
    Subject: Add "complete break ada" test to gdb.ada/complete.exp

The regression had been introduced by:

    commit b5ec771e60c1a0863e51eb491c85c674097e9e13
    Date:   Wed Nov 8 14:22:32 2017 +0000
    Subject: Introduce lookup_name_info and generalize Ada's FULL/WILD name matching

The gist of it is that linespec completion in Ada mode is generating
additional matches that should not appear in the match list
(internally generated symbols, or symbols that should be enclosed
between "<...>").  These extraneous entries have uppercase characters, such as:

    break ada__stringsS
    break ada__strings__R11s
    [etc]

These matches come from minimal symbols.  The problem is that Ada
minsyms end up with no language set (language_auto), and thus we end
up using the generic symbol name matcher for those instead of Ada's.
We already had a special case for in compare_symbol_name to handle
this, but it was limited to expressions, while the case at hand is
completing a linespec.  Fix this by applying the special case to
linespec completion as well.  I.e., remove the EXPRESSION check from
compare_symbol_name.  That alone turns out to not be sufficient still
-- GDB would still show a couple entries that shouldn't be there:

~~
    break ada__exceptions__exception_data__append_info_exception_name__2Xn
    break ada__exceptions__exception_data__exception_name_length__2Xn
~~

The reason is that these minimal symbols end up with their language
set to language_cplus / C++, because those encoded names manage to
demangle successfully as C++ symbols (using an old C++ mangling
scheme):

  $ echo ada__exceptions__exception_data__append_info_exception_name__2Xn | c++filt
  Xn::ada__exceptions__exception_data__append_info_exception_name(void)

It's unfortunate that Ada's encoding scheme doesn't start with some
unique prefix like "_Z" in the C++ Itanium ABI mangling scheme.  For
now, paper over that by treating C++ minsyms as Ada minsyms.

gdb/ChangeLog:
2018-01-10  Pedro Alves  <palves@redhat.com>

        PR gdb/22670
	* ada-lang.c (ada_collect_symbol_completion_matches): If the
	minsym's language is language_auto or language_cplus, pass down
	language_ada instead.
	* symtab.c (compare_symbol_name): Don't frob symbol language here.

gdb/testsuite/ChangeLog:
2018-01-10  Pedro Alves  <palves@redhat.com>

        PR gdb/22670
	* gdb.ada/complete.exp ("complete break ada"): Replace kfail with
	a fail.