Fixed inconsistency between dmap.h and dmap.c: use int instead of int32

Fixed inconsistency between dmap.h and dmap.c: Changed int to int32 in the prototype for DataMapFindArray in dmap.h. This bug prevents users from being able to install davitpy. Specifically, the "sudo python setup.py install" step fails due to an error from gcc. 

This bug only seems to affect 32-bit systems.

Tested this on a fresh install of 32-bit Ubuntu 14.04 and followed the README.md instructions to install davitpy.