add makedefs options for producing individual files

This may be useful for some build environments to avoid parallel make
issues, and artificially-concocted order dependencies, leaving the ordering
up to that specified in the Makefile.

The related makedefs options are now:

       ‐s     Generate the bogusmon , engrave and epitaph files.

       ‐1     Generate the epitaph file.

       ‐2     Generate the engrave file.

       ‐3     Generate the bogusmon file.

Also resolves an existing issue encountered in doc/makedefs.6 where "and epitaphfiles"
was being produced in the result.

doc/makedefs.6

@@ -116,7 +116,26 @@ Generate the
 ,
 .I engrave
 and
-.IR epitaph files.
+.IR epitaph
+files.
+.br
+.TP
+.B -1
+Generate the
+.IR epitaph
+file.
+.br
+.TP
+.B -2
+Generate the
+.IR engrave
+file.
+.br
+.TP
+.B -3
+Generate the
+.IR bogusmon
+file.
 .br
 .TP
 .B -h