The actual compilation process now happens with xbuild. The root makefile
just issues an "xbuild Main.sln" call. If you type 'make' in a subdirectory
you will issue an 'xbuild foo.csproj' for that dir and every subdir. This is
slightly slower than building Main.sln directly if many subdirs are being built.
'make dist' is now implemented with a call to 'git archive' which means our tarball
really does contain everything we need to build monodevelop (yay!).
Makefile integration is now disabled (it's unnecessary).
We now put test assemblies in build/test too to avoid polluting build/bin and build/Addins
