Update autotools toolchain in spatialindex
Replace blank in spatialindex package string

Avoids misquoting issue with Intel compilers.
Use sizeof intrinsic with Intel compilers

ifort does not support c_sizeof, but an equivalent sizeof intrinsic.

When building with Intel, use this intrinsic and define c_sizeof to
be sizeof so we don't have to change the places where it's used.
No need to link mpi_cxx if Python extension module
Only link against -lmpi_f77 when using gfortran