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
VSTUDIO: Fix SDL2 library name for Microvax I debug build
PDP11: Fix DL help attach regression and missing SHOW IOSPACE details
MAKEFILE: Added makefile support for MinGW builds using libSDL2.
H316: Revised standard device implementation from Bob Supnik.

Fixes several bugs described several months ago on the simh list about how the hardware really works, most notably the "dummy" cycle created by an OCP '1 (switch to output mode). In addition, it fixes other problems (OCP '0 and OCP '1 are unconditional) and adds a "busy"
state on character input, like the real hardware.
PDP8: Avoid delaying the initial check for connecctions to mux port after attach.  Fix for #85
Merge latest from Bob Supnik
DISPLAY: Latest version of display code from Phil Budne and Doug Gwyn including initial pdp1_dpy and pdp11_vt
SCP/TMXR: Fix crashing bug when a multiplexer line has logging enabled before a mux attach,