VAX/QVSS: Proper linking on OSX
SCP: Fix SET DEBUG switch interpretation
VAX/QVSS: Added debugging support to sim_video
VIDEO: Moved SDL initialization and cleanup from event thread to the primary thread.

This allows for any errors to be caught more easily and seems to be required on some platforms (OSX).
VIDEO: Move all SDL graphics activities to the background video thread
Fix build warning on OS/X

PDP11/pdp11_io_lib.c: In function 'show_iospace':
PDP11/pdp11_io_lib.c:363: warning: too few arguments for format

PDP10/pdp10_lp20.c: In function 'lp20_set_vfu_type':
PDP10/pdp10_lp20.c:1038: warning: implicit declaration of function
'toupper'
PDP10/pdp10_lp20.c:1121: warning: implicit declaration of function
'isspace'
PDP10: Use system style of include
SCP/VIDEO: Added support for libSDL2 video capabilities.  Changed existing video layer to carry pixels as 32bpp vs 8bpp for more natural behaviors in libSDL2.
SCP/VIDEO: Makefile cleanup for OSX build with libSDL2
Merge pull request #83 from BillHeaton/master

PDP10/11: Fix build warnings on OS/X
Merge remote-tracking branch 'simh/master'
Merge branch 'master' into KDP