various bugfixes from github issues
kmean with some frozen centroids
GPU better tiling for large flat datasets
default AVX for vector ops

* fixes for homebrew and anaconda python

* remove #/bin/bash

* PR feedback and handle different versions of LLVM

Accepting this 2-word PR without CLA....

fix index_cpu_to_gpu_multiple

fix PCA dimension

It took me quite some time to get around this error -- it might save others time.

* make INSTALL a proper markdown file

* add clarification to gpu test

* add forgotten parenthesis

- access GPU resources

- all Hamming distances of all sizes supported

- implemented ScalarQuantizer (without IVF)
- implemented update for IndexIVFFlat
- implemented L2 normalization preproc

- implemented ScalarQuantizer (without IVF)
- implemented update for IndexIVFFlat
- implemented L2 normalization preproc

* moved most FAISS_ASSERT calls to C++ exceptions, and adjusted
  memory allocation to avoid mem leaks

* added an IndexIVFScalarQuantizer type that offers an
  intermediate compression between IVFFlat and IVFPQ

* support removal of indices in IndexIDMap / IndexFlat combination

* various fixes in GPU code

  memory allocation to avoid mem leaks

* added an IndexIVFScalarQuantizer type that offers an
  intermediate compression between IVFFlat and IVFPQ

* support removal of indices in IndexIDMap / IndexFlat combination

* various fixes in GPU code

The rootdir in the distribution seems specific to the creators.  I just made the rootdir for the fvecs be the suggested directory (sift1M) from the installation guide.

correct utils::nextHighestPowerOf2

The bit shift was done as int and not as current type (size_t for example), thus the computed next highest power of 2 was wrong on large numbers.

* add initial cmake support

* update cmake, add cmake instructions to INSTALL

* update findopenmp and INSTALL

* change FindOpenBLAS.cmake to cater for macports

- change cblas.h to openblas_config.h since macports does not ship
cblas.h with openblas.

* revise INSTALL for cmake

Added additional notice concerning compute capabilities.