ubsan: alpha-vms: segv

ubsan: alpha-vms: segv

I thought the fuzzers were really going overboard by defining
VMS_DEBUG but that wasn't the case.  VMS_DEBUG is defined by
default.  Let's not do that, and fix the segv as well.

	* vms.h (VMS_DEBUG): Define as 0.
	* vms-alpha.c (image_write): Move debug output after bounds check.
	Tidy bounds check.
	(_bfd_vms_slurp_eihd): Warning fix.
	(_bfd_vms_slurp_etir): Init variables to avoid bogus warnings.