If two modules contain duplicate class definitions the lookup result can contain
more than 2 elements. Sift the lookup results until we find a field decl.
It is not necessary to do ODR checks in place as they done elsewhere.
This should fix issues when compiling with libstdc++ 5.2 and 6.2.
Patch developed in collaboration with Richard Smith!
llvm-svn: 285184
Vassil Vassilev