Prefer LLVM 3.4 configuration helper if available.
LLVM dropped the mblaze backend in LLVM Subversion revision 187145.
DIDerivedType::getOriginalTypeSize was removed in LLVM Subversion revision 191800.

This is not just a name change; the method is no longer available.  It
has been made into a static helper function in DwarfCompileUnit.  So
presumably it is no longer intended to be used by outside code at all.
LLVM Subversion revision 181632 added support for non-integer, non-type template parameters.
DISubprogram::getReturnTypeName was removed in LLVM Subversion revision 182532.

There does not seem to be any obvious replacement for this functionality.
Some metadata methods now return DIRef<T> or DIDescriptor.

Previously these all returned MDNode pointers.  It looks like these changes
appeared at various times between LLVM 3.3 and 3.4, rather than all at
once.