DOC: Cleanup PDP10 document
sim_BuildROMs: Fix potential memory leaks and a double fclose.
sigma_cpu: Fix always true case

This was the equivalent of "if (vec >= 0x52 || vec <= 0x55)".
sigma_lp: Fix a fopen leak
SAGE: Fix loop bounds in m68k_cpu

cache_line has a size of CACHE_SIZE (16), so starting at that index will be outside the bounds of the array.
SCP: Restructured timer/co-scheduling activities to support co-scheduling on specific timers
SCP: Fixed SEND command to properly support a bare AFTER=n argument.
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.
SCP: Add the # character at the beginning of a line as a comment character.  Requested by Kevin Handy
TMXR, SOCK: Properly declare as const string input only arguments.
SCP: Fix potential infinite loop when EOF is encountered on stdin for hosts using BSDTTY tty I/O.