gdb: Ignore some stringop-overflow and restrict warnings on sparc

gdb: Ignore some stringop-overflow and restrict warnings on sparc

For some reason g++ 11.2.1 on s390x produces a spurious warning for
stringop-overread and restruct in fsb-tdep.c for some memcpy calls.
Add new DIAGNOSTIC_IGNORE_STRINGOP_OVERFLOW and
DIAGNOSTIC_IGNORE_RESTRICT macro to suppress these warning.

include/ChangeLog:

	* diagnostics.h (DIAGNOSTIC_IGNORE_STRINGOP_OVERFLOW): New
	macro.
	(DIAGNOSTIC_IGNORE_RESTRICT): Likewise.

gdb/ChangeLog:

	* fsb-tdep.c (fbsd_make_note_desc): Use
	DIAGNOSTIC_IGNORE_STRINGOP_OVERFLOW and
	DIAGNOSTIC_IGNORE_RESTRICT on sparc.