scripts/mupdfwrap.py: SWIG-compatible support for set_warning_callback() and fz_set_error_callback()
scripts/mupdfwrap.py: SWIG-compatible support for set_warning_callback() and fz_set_error_callback()

We use an intermediate SWIG Director class to allow fz_set_warning_callback()
to call Python via virtual function.

TamirEvan/mupdf,ArtifexSoftware/mupdf,ArtifexSoftware/mupdf,ArtifexSoftware/mupdf,ArtifexSoftware/mupdf,TamirEvan/mupdf,ArtifexSoftware/mupdf,ArtifexSoftware/mupdf,TamirEvan/mupdf,TamirEvan/mupdf,ArtifexSoftware/mupdf,TamirEvan/mupdf,TamirEvan/mupdf,TamirEvan/mupdf,TamirEvan/mupdf,ArtifexSoftware/mupdf