PDP11, VAX: Added ability to set the size of RAUSER devices to be n binary MB (1024*1024) with the -B switch.  Added SHOW -B to display drive capacities in binary MB using the SHOW -B switch.
OSX build: Added more flexible toolchain support for more recent OS X and xCode versions.
OSX build: Revise to fix prior change.
VAX730: Fix 3MB memory setting.  Found by Brad Parker.