- Moved CGI specific lines from configure.in to sapi/cgi/config9.m4

- Moved CGI specific lines from configure.in to sapi/cgi/config9.m4
  which is 'executed' last of the SAPI config.m4's.
- Added --disable-cgi option. (was possible only with above change)
- Made the sed check to not test for the possibly working sed on Solaris
  since that would make the test quite useless. (compile would still fail)

# That sed check is not enabled yet..need to know whether we fail
# during configure or just put out a warning about possible non-working
# sed. As even plain ./configure doesn't work in most cases, I think
# it would be better to just fail during configure and let the users
# fix their paths/install GNU sed.