Checkpoint on calc version 2.12.8.0

Fixed a mistake in "help intro" where some inserted text
    changed the value of "." and thus made the next result
    incorrect.

    Clarified in "help factor" that 1 is returned if no
    factor below the limit was found.

    Removed Makefile variable ${MAKEFILE_REV}.

    The missing cscript/square.calc file has been restored.

    Fixed compiler errors and warnings related to GCC.
    In particular, gcc/9.3.1 and gcc/10.2.1 now compile
    calc without any compiler errors or warnings,
    even with -Werror -Wextra -pedantic.

    To print out information about the calc compliation
    environment, we added the following make rule:

	make calcinfo

    Improved how 'make debug' operates.

    Moved help/contrib to CONTRIB-CODE.  The help/contrib file
    is now build from a copy of CONTRIB-CODE.

    Created a new calc bug report Email address.  Created a new calc
    question Email address.  Created a new calc contribution Email
    address.  See the BUGS file for details.

    Added "help questions" to print the QUESIONS help file.

    If the environment variable $CALCHELP is defined and is non-empty,
    then calc help files will be in the direcgory by the $CALCHISTFILE
    environment variable.

    If the environment variable $CALCCUSTOMHELP is defined and is
    non-empty, then custom calc help files will be in the direcgory
    by the $CALCCUSTOMHELP environment variable.

    The calc-tester mailing list has been retired.  See:

	* How to submit a calc bug report:

	    http://www.isthe.com/chongo/tech/comp/calc/calc-bugrept.html

	* How to contribute code to calc:

	    http://www.isthe.com/chongo/tech/comp/calc/calc-contrib.html

	* How to submit a question about calc:

	    http://www.isthe.com/chongo/tech/comp/calc/calc-question.html

calc.c

@@ -1,7 +1,8 @@
 /*
  * calc - arbitrary precision calculator
  *
- * Copyright (C) 1999-2013  David I. Bell, Landon Curt Noll and Ernest Bowen
+ * Copyright (C) 1999-2013,2021  David I. Bell, Landon Curt Noll
+ *				 and Ernest Bowen
  *
  * Primary author:  David I. Bell
  *
@@ -403,7 +404,7 @@ main(int argc, char **argv)
 								" long");
 							exit(18);
 						}
-						/* XXX What if *cp = '\''? */
+						/* XXX - what if *cp = '\''? */
 						*bp++ = '\'';
 						strncpy(bp, cp, len+1);
 						bp += len;