Fix 'Bug 3' where too long SYMBOL=string in run-time config file could
overflow a local buffer and clobber the stack.
Valid value is only one character long after processing an 'escaped'
encoded character which can be at most 6 characters (plus terminator):
backslash M backslash and up three digits. If/when UTF8 gets added
the number of digits will increase. Use a truncated copy of the input
(substantially bigger than 6+1); ignore any excess.
Fix 'Bug 2' where too long MENUCOLOR=string in run-time config file
could overflow a local buffer and clobber the stack.
Theoretically a menu coloring regular expression could require a
bigger buffer but I don't think we need to try to support that.
255 characters minus the amount needed to specify color and/or
attributes should be ample.
