Support use of dlib a cross-compiled ExternalProject

the former works with a wider range of tools in the STL.

This follows convention which simplifies using dlib as a CMake
ExternalProject.

since sometimes gfortran isn't available and openblas should already be linked
to gfortran if it was needed.

orthogonalize does not work with fixed-sized matrices

detect OS X, and query sysconfig for libdir

global functions.

CMake.

a little bit.

Drectangle equality

Only issue is that the strong is hardcoded - otherwise
this is actually technically required by PEP 396

Add a simple print and serialization scheme for
shape_predictor_training_options. This enables you to serialize
your training options.

Easy change to allow comparisons on the Python side for
both rectangle and drectangle

This is in the main dlib source code (rather than specifically
Python). Equality operators were missing for drectangles and
so were copied from rectangle.

often create a conflict with MATLAB's copy of the MKL.