diagnostics: unbreak 'make gcc.pot'

As noted by Joseph, I broke "make gcc.pot" in r14-6057-g12b67d1e13b3cf
by adding an overloaded format API with the format string in a different
position, leading to this failure:

emit_diagnostic_valist used incompatibly as both --keyword=emit_diagnostic_valist:4
--flag=emit_diagnostic_valist:4:gcc-internal-format and --keyword=emit_diagnostic_valist:5
--flag=emit_diagnostic_valist:5:gcc-internal-format

Fix by replacing the overloaded function with one with a different name.

See also r10-6297-g6c8e584430bc5d for previous fixes for this involving
the same function, or r5-6946-g40fecdd62f7d29 and
r5-6959-gdb30e21cbff7b9 for older fixes for similar issues.

gcc/analyzer/ChangeLog:
	* pending-diagnostic.cc (diagnostic_emission_context::warn):
	Update for renaming of emit_diagnostic_valist overload to
	emit_diagnostic_valist_meta.
	(diagnostic_emission_context::inform): Likewise.

gcc/ChangeLog:
	* diagnostic-core.h (emit_diagnostic_valist): Rename overload
	to...
	(emit_diagnostic_valist_meta): ...this.
	* diagnostic.cc (emit_diagnostic_valist): Likewise, to...
	(emit_diagnostic_valist_meta): ...this.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>