Automatically do the equivalent of freeMachineCodeForFunction(F) when F is

being destroyed. This allows users to run global optimizations like globaldce
even after some functions have been jitted.

This patch also removes the Function* parameter to
JITEventListener::NotifyFreeingMachineCode() since it can cause that to be
called when the Function is partially destroyed. This change will be even more
helpful later when I think we'll want to allow machine code to actually outlive
its Function.

llvm-svn: 85182