man: generate manpages from .org files

Generate the manpages from org-documents which makes it a bit easier to
keep them update to date since I find org-syntax easier than troff, and
we can use include files.

man/exit-code.inc

@@ -0,0 +1,9 @@
+* EXIT CODE
+
+This command returns 0 upon successful completion, or a non-zero exit code
+otherwise.
+
+
+# Local Variables:
+# mode: org
+# End: