Introduce needsCodegen.

This is a backport of the code from 2.065.
Travis: Further split up multilib release test runs due to time limit.
Merge pull request #639 from klickverbot/multilib-split

Travis: Further split up multilib release test runs due to time limit.
Merge branch 'merge-2.064'.
Merged ldc-developers/druntime#10.
llvm::error_code was replaced by std::error_code in LLVM 3.5
Fix inclusion of LLVM config file.

llvm/Config/config.h is now private. I still need to check if this include is really required for LLVM 3.3/3.4.
Merge branch 'master' into merge-2.065

Conflicts:
	dmd2/declaration.h
	dmd2/dsymbol.h
	dmd2/func.c
	gen/functions.cpp
	gen/toir.cpp
	runtime/druntime