MAINT: update release scripts for building OS X binaries.

Works with Python 3.x now that bdist_mpkg is ported (thanks @matthew-brett).
BUG: Fix issue with PR #3491

Don't convert unicode string to ascii string before getting byte length. Also, get length of non string type as ascii or unicode depending on output string type.
Merge pull request #3761 from ContinuumIO/2890_fix

Fix for PR #3491
BUG: make checking for sse intrinsics more robust

check for two intrinsics from [ex]mmintrin.h instead of only checking
the existance of the headers.
E.g. mingw 4.2 emmintrin.h can be included even if SSE2 is disabled.
closes #3760
Merge pull request #3780 from juliantaylor/sse-configure-check-1.8.x

Backport PR 3772
BLD: Backport Ralf's gh-3766 fixes to the bento build scripts.

The original PR included fixes for ufunc_override that are not
needed for 1.8, so I just copied the files numpy/core/bento.info and
numpy/core/bscript from master.
TST: wrong indent in multiarray tests
ENH: Add gfortran to travis.yml configuration to enable f2py.

The f2py tests would not run without gfortran.
Merge pull request #3786 from charris/backport-1.8-3773

Backport 1.8 3773
Merge pull request #3785 from charris/backport-1.8-3781

Backport 1.8 3781
Merge pull request #3784 from charris/backport-1.8-3766

Backport 1.8 3766