Pass Distutils OPT config variable to ./configure

The OPT config variable contains compiler flags relating to the target
architecture and the optimization level. These should be passed through
to the bundled ./configure scripts.

Addresses #97.
Pass CFLAGS from Distutils as CFLAGS and CXXFLAGS
Merge pull request #98 from lpsinger/pass_more_cflags_to_configure

Pass more cflags to configure