Consolidate compiler configurations into get_distconfig

Also,
1. Provides a way to build MPI Cython extensions which uses sequential fftw
   library.
2. Should prevent KeyError if variable is missing in distutils.sysconfig.
   Fixes #29
2 jobs for topic/default/site-distutils-sysconfig in 5 minutes and 19 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed tests #140524

00:04:03

passed tests_pythran_mpi #140525

00:05:19