VMS is a historically 32bit operating system in a 64bit world and
with the need to retain binary compatibility with old applications. The
stack remains forever 32bit but the heap can be either 32bit or 64bit. A
logical name (aka environment variable) is currently used to switch 
between, but was considered too coarse, so a binder switch is 
introduced: -Hnn where nn is 32 or 64 to lock an image to a particular 
heap regardless of the logical name setting.

Tested on x86_64-pc-linux-gnu, committed on trunk

2010-06-23  Doug Rupp  <rupp@adacore.com>

	* bindusg.adb (Display): Write -Hnn line.
	* bindgen.adb (Gen_Adainit_Ada): Write Heap_Size to binder file as 
	necessary.
	* init.c (__gl_heap_size): Rename from __gl_no_malloc_64 and change
	valid values to 32 and 64.
	(GNAT$NO_MALLOC_64): Recognize TRUE, 1, FALSE, and 0 in addition to
	ENABLE, DISABLE as valid settings.
	* switch-b.adb (Scan_Binder_Switches): Process -Hnn switch.
	* memtrack-vms_64.adb (Gnat_Heap_Size): Rename from Gnat_No_Malloc64
	and change valid values to 32 and 64.
	* s-memory-vms_64.adb (Gnat_Heap_Size): Likewise.
	* opt.ads (Heap_Size): New global variable.
	* gcc-interface/utils2.c (maybe_wrap_malloc): Remove mostly redundant 
	TARGET_MALLOC64 check. Fix comment.