document prompt in shell script mode, fix man formatting, legacy awk

Documented unexpected behavior when calc is running in
"shell script mode" and the prompt builtin function is used
without the -p flag.  Updated help/prompt, help/unexpected
and the calc man page accordingly.

Unless calc is given the -p command line option, calc will reopen
stdin as /dev/null instead of just closing stdin.  This prevents
subsequent opens grabbing the 1st file descriptor.

Disable regress tests 4709, 4710, and 7763 because they print
multi-byte sequences, which are just fine for calc, the awk
used to evaluate the regression suite output in some legacy
systems report a "multibyte conversion failure".

Added a number of missing Makefile variables to the "make env" rule.

The man command is used to format the calc.1 man page into calc.usage.

The "help calc" command now prints the formatted calc man page (calc.usage).
The "help man" command now prints the formatted calc man page (calc.usage).
The "help usage" command now prints the formatted calc man page (calc.usage).

The file, calc.cat1, is formed by gzipping the calc.usage
formatted man page.  The calc.cat1 is installed as the calc
cat section 1 man page.

Updated the Copyright string in version.c to refer to
the COPYING file and the "help copying" command.

Added calc.cat1 to .gitignore.  Using "sort -d -u" to sort .gitignore content.

Avoiding use of modern [[ and ]] in Makefile for those legacy systems
whose shell do not support them.  *sigh*

Fixed the order of "help full" to match the order of topics listed
buy the "help help" command.

Sorted the halias[] help topics table in help.c using sort -d -u.

calc.man

@@ -470,6 +470,24 @@ The
 flag overrides
 .BR \-i .
 
+.sp 1
+When running calc as a shell script (see
+.B "SHELL SCRIPT MODE"
+for details), calc will close standard input (stdin)
+during startup
+.B UNLESS
+the
+.B \-p
+flag is given on the command line.
+When calc is running in
+.BR "shell script mode" ,
+shell scripts that call the
+.BR prompt (str)
+builtin will not work properly (the prompt builtin
+will always fail) unless the
+.B \-p
+flag is given on the command line.
+
 .TP
 .B \-q
 Disable the reading of the startup scripts.
@@ -651,7 +669,9 @@ echo chongo was here | calc \-i 'print fgetline(files(0));'
 .fi
 .in -5n
 .sp 1
-This is because without \-p, the interactive parser, in an effort
+This is because without
+.BR \-p ,
+the interactive parser, in an effort
 to parse interactive commands, flushes data on standard input.
 
 .PP
@@ -932,6 +952,67 @@ whereas
 .sp 1
 will not.
 
+.sp 1
+By default, using calc startup in
+.BR "shell script mode" ,
+calc will close standard input (stdin).
+Thus builtin functions such as
+.BR prompt (str)
+will fail (return a null value).
+Calc shell scripts that call the
+.BR prompt (str)
+builtin will not work properly (the prompt builtin
+will always fail and return a null value) unless the
+.B \-p
+flag is given on the command line.
+
+.sp 1
+The following shell script will always print "got null" because
+stdin will be closed by calc during startup:
+
+.sp 1
+.in +5n
+.nf
+#!/usr/bin/calc \-q \-f
+
+# The prompt will ALWAYS FAIL and return a null value
+n = prompt("Test> ");
+if (isnull(n)) {
+  print("got null");
+} else {
+  print("got " + n);
+}
+.fi
+.in -5n
+.sp 1
+However the following shell script (note the
+.B \-p
+before the
+.B \-f
+in the 1st line) will be interactive, prompt with "Test> " and print
+the "got" result as expected:
+
+.sp 1
+.in +5n
+.nf
+#!/usr/bin/calc \-q \-p \-f
+
+n = prompt("Test> ");
+if (isnull(n)) {
+  print("got null");
+} else {
+  print("got " + n);
+}
+.fi
+.in -5n
+
+.sp 1
+Note in the example above, the
+.B \-p
+flag must be given before the final
+.B \-f
+command line flag.
+
 .PP
 
 .SH DATA TYPES