Fix c/InternFunctionWeakref.c.

The test was failing when building with gcc 4.8. It looks like weakrefs are
reachable via emit_cgrah_aliases and emit_cgraph_weakref. This causes us to
try to use rauw twice, causing an assert when we get a this->rauw(this).

The patch simply skips weakrefs in emit_cgrah_aliases.

git-svn-id: https://llvm.org/svn/llvm-project/dragonegg/trunk@208003 91177308-0d34-0410-b5e6-96231b3b80d8