Further re-unification of code duplicated across mod_cgi/mod_cgid into

Further re-unification of code duplicated across mod_cgi/mod_cgid into
cgi_common.h.  Functional changes:

- brings the PR 61980 fix to mod_cgid as well, and
- some mod_cgid-specific APLOGNOs are dropped in favour of the
  code used in the equivalent error path in mod_cgi

... otherwise no user-visible changes (intended).

* modules/generators/cgi_common.h (log_scripterror, log_script_err): Move
  here from mod_cgi.
  (cgi_handle_exec): Move here, renamed from mod_cgi's handle_exec.
  (cgi_optfns_retrieve): New function, split out from mod_cgi's cgi_post_config.

* modules/generators/mod_cgid.c: Adjust accordingly, update to pass
  logno separately.
  (register_hooks): Register cgi_optfns_retrieve.

* modules/generators/mod_cgi.c: Adjust accordingly.
  (register_hooks): Register cgi_optfns_retrieve.

Github: closes #141

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1881559 13f79535-47bb-0310-9956-ffa450edef68