Remove Support/IncludeFile.h and its only user. This is actively harmful, since
it breaks the modules builds (where CallGraph.h can be quite reasonably
transitively included by an unimported portion of a module, and CallGraph.cpp
not linked in), and appears to have been entirely redundant since PR780 was
fixed back in 2008.

If this breaks anything, please revert; I have only tested this with a single
configuration, and it's possible that this is still somehow fixing something
(though I doubt it, since no other similar file uses this mechanism any more).
[MCJIT] Replace a c-style cast with reinterpret_cast + static_cast.

C-style casts (and reinterpret_casts) result in implementation defined
values when a pointer is cast to a larger integer type. On some platforms
this was leading to bogus address computations in RuntimeDyldMachOAArch64.

This should fix http://llvm.org/PR20501.