Support optional features of MatIO on Windows and Mac

The Windows binary currently comes with a matio compiled without zlib and HDF5, which means that it cannot read/write compressed MAT files nor 7.3 MAT-files.

The Mac binary is in the same situation.

Fixing this would first require compiling static versions of zlib and HDF5 for the 2 platforms. Then -lhdf5 -lz would have to be added to LIBADD_MATIO or, better, we could use pkg-config in ax_matio.m4 to detect the proper link flags (but the latter may be difficult in a cross-compiler environment).