Introduce common/gdb_setjmp.h

Introduce common/gdb_setjmp.h

This commit creates a new file, common/gdb_setjmp.h, to hold some
portability macros for setjmp/longjmp et al. that are used by the
exceptions subsystem and by the demangler crash catcher.

gdb/ChangeLog:

	* common/gdb_setjmp.h: New file.
	* Makefile.in (HFILES_NO_SRCDIR): Add common/gdb_setjmp.h.
	* configure.ac: Move sigsetjmp check...
	* common/common.m4: ...here.
	* configure: Regenerate.
	* cp-support.c (SIGJMP_BUF): Delete.
	(SIGSETJMP): Likewise.
	(SIGLONGJMP): Likewise.
	* exceptions.h (gdb_setjmp.h): Include.
	(setjmp.h): Do not include.
	(EXCEPTIONS_SIGJMP_BUF): Delete.
	(EXCEPTIONS_SIGSETJMP): Likewise.
	(EXCEPTIONS_SIGLONGJMP): Likewise.
	Replace all uses of EXCEPTIONS_SIG* macros with SIG* macros
	from gdb_setjmp.h.
	* exceptions.c: Likewise.

gdb/gdbserver/ChangeLog:

	* config.in: Regenerate.
	* configure: Likewise.