alpha-vms: error paths not freeing memory and malloc result checks

When realloc fails it doesn't free the old memory.  In BFD we usually
will exit with an error on a realloc fail, so want to tidy up memory
on error paths.  That's done by bfd_realloc_or_free.

	* vms-alpha.c (vms_get_remaining_object_record): Use
	bfd_realloc_or_free rather than bfd_realloc.
	(add_symbol_entry, vector_grow1, alpha_vms_slurp_relocs): Likewise.
	(dst_define_location, parse_module): Likewise, and check realloc
	return status before using memory.  Return status from function
	adjusting all callers.