a bug where the reference count is copied in the copy constructor, which means that there were cases when the CompilerInvocation
objects created by ASTUnit were actually leaked. When I fixed that bug locally, it showed that a whole bunch of code assumed
that the LangOptions object that was part of CompilerInvocation was still alive. By making it heap-allocated and reference counted,
we can keep it around after the CompilerInvocation object goes away.
As part of this change, change CompilerInvocation:getLangOptions() to return a pointer, acting as another clue that this
object may outlive the CompilerInvocation object.
This commit doesn't fix the CompilerInvocation leak itself. That will come when I commit the fix to llvm::RefCountedBase<T> to
mainline LLVM.
llvm-svn: 144930
8cf47df72f