Improve warning suppression for inlined functions [PR98512].

Improve warning suppression for inlined functions [PR98512].

Resolves:
PR middle-end/98871 - Cannot silence -Wmaybe-uninitialized at declaration site
PR middle-end/98512 - #pragma GCC diagnostic ignored ineffective in conjunction with alias attribute

gcc/ChangeLog:

	PR middle-end/98871
	PR middle-end/98512
	* diagnostic.c (get_any_inlining_info): New.
	(update_effective_level_from_pragmas): Handle inlining context.
	(diagnostic_enabled): Same.
	(diagnostic_report_diagnostic): Same.
	* diagnostic.h (struct diagnostic_info): Add ctor.
	(struct diagnostic_context): Add new member.
	* tree-diagnostic.c (set_inlining_locations): New.
	(tree_diagnostics_defaults): Set new callback pointer.