Make gdb.base/dmsym.exp independent of "set language ada"

Make gdb.base/dmsym.exp independent of "set language ada"

This test is using "set language ada" expecting that to cause GDB to
do Ada symbol name matching.  That won't work when GDB uses the
symbol's language to decide which symbol matching algorithm to use,
because the test's symbols are C symbols.

So generalize the test a bit to not rely on Ada name matching rules.

Confirmed that by undoing the original fix the test was written for,
the test still fails.

gdb/testsuite/ChangeLog:
2017-07-20  Pedro Alves  <palves@redhat.com>

	* gdb.base/dmsym.c (pck__foo__bar__minsym): Rename to ...
	(test_minsym): ... this, and make static.
	(get_pck__foo__bar__minsym): Rename to ...
	(get_test_minsym): ... this.
	* gdb.base/dmsym.exp (): Remove "set language ada" call.  Adjust
	symbol names and comments.
	* gdb.base/dmsym_main.c (get_pck__foo__bar__minsym): Rename to ...
	(get_test_minsym): ... this.
	(pck__foo__bar__minsym__2): Rename to ...
	(test_minsym): ... this.
	(main): Adjust.