use int64_t for idx type if --enable-64 * configure.ac: Check for and use int64_t instead of long if --enable-64. (IDX_TYPE_LONG): Delete definion. Change all uses to check USE_64_BIT_IDX_T instead. * MArray-i.cc: Instantiate arrays of int64_t instead of long, but only if USE_64_BIT_IDX_T is defined. * acinclinde.m4 (OCTAVE_CHECK_SIZEOF_FORTRAN_INTEGER): Use int64_t instead of long.