asan: vms-alpha: heap-buffer-overflow

asan: vms-alpha: heap-buffer-overflow

Two buffer overflows, and some over restrictive length checks.

	* vms-alpha.c (add_symbol): Add "max" parameter.  Error on string
	length larger than max.
	(_bfd_vms_slurp_egsd): Ensure record is at least large enough to
	read string length byte, error if not.  Pass size to add_symbol.
	(_bfd_vms_slurp_etir): Don't read past end of buffer when reading
	type and length.  Allow read of last byte in buffer.