gdb/testsuite: eliminate gdb_suppress_tests mechanism

gdb/testsuite: eliminate gdb_suppress_tests mechanism

There is a lot of support code for the test suppression mechanism.  But
as far as I know, it is not useful.  The gdb_suppress_tests proc is in
fact disabled with this comment that has been there since forever:

    return;  # fnf - disable pending review of results where
             # testsuite ran better without this

I suggest to just remove everything related to test suppression, that
removes some unnecessary complexity from the support code and the tests.

gdb/testsuite/ChangeLog:

	* lib/gdb.exp (gdb_test_multiple): Remove things related to test
	suppression.
	(default_gdb_exit): Likewise.
	(default_gdb_spawn): Likewise.
	(send_gdb): Likewise.
	(gdb_expect): Likewise.
	(gdb_expect_list): Likewise.
	(default_gdb_init): Likewise.
	(gdb_suppress_entire_file): Remove.
	(gdb_suppress_tests): Remove.
	(gdb_stop_suppressing_tests): Remove.
	(gdb_clear_suppressed): Remove.
	* lib/mi-support.exp (mi_uncatched_gdb_exit): Remove things
	related to test suppression.
	(default_mi_gdb_start): Likewise.
	(mi_gdb_reinitialize_dir): Likewise.
	(mi_gdb_test): Likewise.
	(mi_run_cmd_full): Likewise.
	(mi_runto_helper): Likewise.
	(mi_execute_to): Likewise.
	* lib/prompt.exp (default_prompt_gdb_start): Likewise.
	* gdb.base/bitfields.exp: Likewise.
	* gdb.base/bitfields2.exp: Likewise.
	* gdb.base/break.exp: Likewise.
	* gdb.base/call-sc.exp: Likewise.
	* gdb.base/callfuncs.exp: Likewise.
	* gdb.base/dfp-test.exp: Likewise.
	* gdb.base/endian.exp: Likewise.
	* gdb.base/exprs.exp: Likewise.
	* gdb.base/funcargs.exp: Likewise.
	* gdb.base/hbreak2.exp: Likewise.
	* gdb.base/recurse.exp: Likewise.
	* gdb.base/scope.exp: Likewise.
	* gdb.base/sepdebug.exp: Likewise.
	* gdb.base/structs.exp: Likewise.
	* gdb.base/until.exp: Likewise.
	* gdb.cp/misc.exp: Likewise.

Change-Id: Ie6d3025091691ba72010faa28b85ebd417b738f7