[trac1687]Revert "[trac1687] make man page generation on by default"

This reverts commit 682df53277cfb545a1ba34a3a2198cb555cca6f5.

Decided to not enable documentation by default for now.
Need to handle build machines and make sure the doc generation
environment is in place first.

configure.ac

@@ -966,8 +966,8 @@ AC_SUBST(PERL)
 AC_PATH_PROGS(AWK, gawk awk)
 AC_SUBST(AWK)
 
-AC_ARG_ENABLE(man, [AC_HELP_STRING([--disable-man],
-  [don't generate documentation])], enable_man=$enableval, enable_man=yes)
+AC_ARG_ENABLE(man, [AC_HELP_STRING([--enable-man],
+  [regenerate man pages [default=no]])], enable_man=$enableval, enable_man=no)
 
 AM_CONDITIONAL(ENABLE_MAN, test x$enable_man != xno)