* c-pragma.c (handle_pragma_diagnostic): New.
(init_pragma): Register it.
* doc/extend.texi: Document it.

* diagnostic.def: Add DK_UNSPECIFIED and DK_IGNORED.
* diagnostic.h (diagnostic_classify_diagnostic): Declare.
(diagnostic_context): Add classify_diagnostic[].
* diagnostic.c (diagnostic_count_diagnostic): Don't count warnings
as errors if they're overridden to DK_WARNING.
(diagnostic_initialize): Initialize classify_diagnostic[].
(diagnostic_set_kind_override): New.
(diagnostic_report_diagnostic): Check for kind changes.
* opts.c (common_handle_option): Take lang_mask.  Update callers.
Handle OPT_Werror_.
* common.opt (Werror=): New.
* doc/invoke.texi: Document -Werror=*

From-SVN: r109907