TECO-64 version 200.21.0

Added more test scripts and test cases.
Fixed bugs, deficiencies, and incompatibilities found through testing.
Renamed --buffer and -B options to --text and -T, respectively.
Enhanced at-sign text arguments to allow paired parentheses and brackets, in addition to braces.
-W restores display colors previously set with F1/F2/F3 commands.
^N command returns -1 instead of 1 if at EOF.
^Q command returns correct count instead of 0.
m,nS now works correctly, and does not move dot on failure.
Added bit to ED flag to control handling of NUL chrs. in input files.
Added bit to E1 flag to allow LF to terminate command string.
Added rudimentary HELP support (w/ immediate NYI error).