BUG: fix g77 ABI detection for scipy.lib.blas.

This is the last code that did not use our consolidated code in
_build_utils. With this patch, building scipy with MKL on OS X passes
the test suite.
Merge pull request #524 from cournape/fix_scipy_lib_veclib_detection

BLD: lib: fix g77 ABI detection for scipy.lib.blas.