use new FFI based mupdf API

This will use the new API where the Lua/C interface was used before
and also drop usage of mupdfimg wrapper which is now implemented
within the mupdf interface
update to latest base
fix renderImage invocation
Merge pull request #4 from chrox/fix_1014

fix renderImage invocation
Merge pull request #1014 from hwhw/master

use new FFI based mupdf API