Fixed an issue where we could end up creating multiple

C++ methods for a function depending on how the DWARF was 
created. Now we parse the class type from the definition,
and all methods that use DW_AT_specification or DW_AT_abstract_origin
attributes to point to the definition, now won't create
duplicate entries. This is in response to how clang++ creates
much different DWARF than gcc.

llvm-svn: 137737