[LLVM-C] Consolidate llgo's DIBuilder Bindings

Summary: Move and correct LLVMDIBuilderCreateTypedef.  This is the last API in DIBuilderBindings.h, so it is being removed and the C API will now be re-exported from IRBindings.h.

Reviewers: whitequark, harlanhaskins, deadalnix

Reviewed By: whitequark

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D46725

llvm-svn: 332041