Fix build for Visual Studio on Windows.
Fix build for Visual Studio on Windows.

void * arithmetic is a gcc extension. Cast the pointer to avoid compilation errors.

pombredanne/datrie,kmike/datrie,pombredanne/datrie,kmike/datrie,kmike/datrie,tpn/datrie,pyparallel/datrie,hickford/datrie,hickford/datrie,tpn/datrie,tpn/datrie,pombredanne/datrie,hickford/datrie,pyparallel/datrie,pyparallel/datrie