METIS errors in GraphEO on MacOS 10.8

Errors when compiled with 64-bit METIS on MACOSX; complains about long long \* to int\* conversion in GraphEO. This is caused by using int\* in INDDGO but idx_t\* in METIS. INDDGO code should be revised to use idx_t for full compatibility. 

Current workaround: compile METIS with 32 bit ints.
