Currently the temporary directory used for modules is under the current
directory; this patch changes it so a temp directory is used; so we
could build the apidocs with a R/O filesystem.

Reviewed-by: ultrotter

Reviewed-by: imsnah

The patch adds the apidoc target and the epydoc config file for it. Note
that this is for epydoc 3.0 and that it will put the docs into
./doc/api/.

The patch also adds a new .gitignore rule for the auto-generated rapi
fragment.

Reviewed-by: imsnah