support Ada EH ABI v1

support Ada EH ABI v1

A new pair of hooks used by Ada exception handlers, for correct
release of reraised exception occurrences, involves the introduction
of new v1 symbols that GDB should use when available.  The older, v0
ABI remains available in newer runtimes for bootstrapping purposes
only.

for  gdb/ChangeLog

	* ada-lang.c (exception_support_info_v0): Renamed from...
	(default_exception_support_info): ... this.  Create new
	definition for v1.
	(ada_has_this_exception_support): Look up catch_handlers_sym.
	(ada_exception_support_info_sniffer): Try v0 after default.