Cross compiling.

[Amar Takhar]

Cross compiling works.  Usage is really simple:

  waf configure --cross-compiler=/path/to/cross/cc

Use --cross-cflags and --cross-ldflags as necessary.

I'll be hooking up an ARM cross build to buildbot that will download and run on 
one of the RPI2s I have here to ensure the cross compiling actually works.

Snapshots will be up soon too.  These will be generated only if all builds 
succeed.


Amar.