Remove OriginalTypeParmDecl; the original type is the one specified

in the DeclaratorInfo, if one is present.

Preserve source information through template instantiation.  This is made
more complicated by the possibility that ParmVarDecls don't have DIs, which
is possibly worth fixing in the future.

Also preserve source information for function parameters in ObjC method
declarations.

llvm-svn: 84971