[Bf-committers] For MinGW builders

[Antony Riakiotakis]

Cycles, OpenEXR and LibMV are supported now. OpenCollada and FFMpeg
still remaining.

Also Scons support was added. Just like MSVC a 64 build of python will
build for 64 bits.

Unfortunately, for cycles I still haven't managed to get the CUDA
binaries building. Looks like a 64bit MSVC environment is needed, same
as with 32 bit MinGW :(.

In any case, happy benchmarking!