[mono] fix size of gbooleans struct members
[mono] fix size of gbooleans struct members

They are 32bit integers so don't marshal them as 1 byte integers.
Fixes corrupt data when transferring tracks.

neuschaefer/libgpod,hyperair/libgpod,hyperair/libgpod,neuschaefer/libgpod,neuschaefer/libgpod,hyperair/libgpod,neuschaefer/libgpod,hyperair/libgpod,hyperair/libgpod,neuschaefer/libgpod