Demangler crash handler

Demangler crash handler

This commit wraps calls to the demangler with a segmentation fault
handler.  The first time a segmentation fault is caught a core file
is generated and the user is prompted to file a bug and offered the
choice to exit or to continue their GDB session.  A maintainence
option is provided to allow the user to disable the crash handler
if required.

gdb/
2014-06-19  Gary Benson  <gbenson@redhat.com>

	* configure.ac [AC_CHECK_FUNCS] <sigaltstack>: New check.
	* configure: Regenerate.
	* config.in: Likewise.
	* main.c (signal.h): New include.
	(setup_alternate_signal_stack): New function.
	(captured_main): Call the above.
	* cp-support.c (signal.h): New include.
	(catch_demangler_crashes): New flag.
	(SIGJMP_BUF): New define.
	(SIGSETJMP): Likewise.
	(SIGLONGJMP): Likewise.
	(gdb_demangle_jmp_buf): New static global.
	(gdb_demangle_attempt_core_dump): Likewise.
	(gdb_demangle_signal_handler): New function.
	(gdb_demangle): If catch_demangler_crashes is set, install the
	above signal handler before calling bfd_demangle, and restore
	the original signal handler afterwards.  Display the offending
	symbol and call demangler_warning the first time a segmentation
	fault is caught.
	(_initialize_cp_support): New maint set/show command.

gdb/doc/
2014-06-19  Gary Benson  <gbenson@redhat.com>

	* gdb.texinfo (Maintenance Commands): Document new
	"maint set/show catch-demangler-crashes" option.