This patch introduces a verbosity level to dump messages:
"user-facing" vs "internals".

By default, messages at the top-level dump scope are "user-facing",
whereas those that are in nested scopes are implicitly "internals",
and are filtered out by -fopt-info unless a new "-internals" sub-option
of "-fopt-info" is supplied (intended purely for use by GCC developers).
Dumpfiles are unaffected by the change.

Given that the vectorizer is the only subsystem using AUTO_DUMP_SCOPE
(via DUMP_VECT_SCOPE), this only affects the vectorizer.

Filtering out these implementation-detail messages goes a long way
towards making -fopt-info-vec-all more accessible to advanced end-users;
the follow-up patch restores the most pertinent missing details.

gcc/ChangeLog:
	* doc/invoke.texi (-fopt-info): Document new "internals"
	sub-option.
	* dump-context.h (dump_context::apply_dump_filter_p): New decl.
	* dumpfile.c (dump_options): Update for renaming of MSG_ALL to
	MSG_ALL_KINDS.
	(optinfo_verbosity_options): Add "internals".
	(kind_as_string): Update for renaming of MSG_ALL to MSG_ALL_KINDS.
	(dump_context::apply_dump_filter_p): New member function.
	(dump_context::dump_loc): Use apply_dump_filter_p rather than
	explicitly masking the dump_kind.
	(dump_context::begin_scope): Increment the scope depth first.  Use
	apply_dump_filter_p rather than explicitly masking the dump_kind.
	(dump_context::emit_item): Use apply_dump_filter_p rather than
	explicitly masking the dump_kind.
	(dump_dec): Likewise.
	(dump_hex): Likewise.
	(dump_switch_p_1): Default to MSG_ALL_PRIORITIES.
	(opt_info_switch_p_1): Default to MSG_PRIORITY_USER_FACING.
	(opt_info_switch_p): Update handling of default
	MSG_OPTIMIZED_LOCATIONS to cope with default of
	MSG_PRIORITY_USER_FACING.
	(dump_basic_block): Use apply_dump_filter_p rather than explicitly
	masking the dump_kind.
	(selftest::test_capture_of_dump_calls): Update test_dump_context
	instances to use MSG_ALL_KINDS | MSG_PRIORITY_USER_FACING rather
	than MSG_ALL.  Generalize scope test to be run at all four
	combinations of with/without MSG_PRIORITY_USER_FACING and
	MSG_PRIORITY_INTERNALS, adding examples of explicit priority
	for each of the two values.
	* dumpfile.h (enum dump_flag): Add comment about the MSG_* flags.
	Rename MSG_ALL to MSG_ALL_KINDS.  Add MSG_PRIORITY_USER_FACING,
	MSG_PRIORITY_INTERNALS, and MSG_ALL_PRIORITIES, updating the
	values for TDF_COMPARE_DEBUG and TDF_ALL_VALUES.
	(AUTO_DUMP_SCOPE): Add a note to the comment about the interaction
	with MSG_PRIORITY_*.
	* tree-vect-loop-manip.c (vect_loop_versioning): Mark versioning
	dump messages as MSG_PRIORITY_USER_FACING.
	* tree-vectorizer.h (DUMP_VECT_SCOPE): Add a note to the comment
	about the interaction with MSG_PRIORITY_*.

gcc/testsuite/ChangeLog:
	* gcc.dg/plugin/dump-1.c: Update expected output for test_scopes
	due to "-internals" not being selected.
	* gcc.dg/plugin/dump-2.c: New test, based on dump-1.c, with
	"-internals" added to re-enable the output from test_scopes.
	* gcc.dg/plugin/plugin.exp (plugin_test_list): Add dump-2.c.

From-SVN: r264851