For PR1142:

When an unresolved definition is found, check to see if it is only unresolved
because the csretcc was upgraded to the sret param attribute. Such changes
change the function type and lead to unresolved definitions. In such cases, just
cast the function to the type expected by the CallInst. That is, cast to the
version of the function that has the sret param attribute.

llvm-svn: 33623