SCP: Fixed EXPECT processing to properly cleanup after matches.  Added display of expect buffer to SHOW EXPECT and extended expect match debugging output.
SCP: Added expansion of special built-in environment variable DATE_YC which is the century of the current date.
SCP: Fix simh console session output of remote console commands to avoid stairstepping as described in issue #165
makefile: Removed dependence on libSDL for simulators which don't need SDL support.  Fix #164 Suggested by Rhialto.
Merge remote-tracking branch 'upstream/master'