When IRgen refers to a function declaration that is not a definition,

and we later find the definition, make sure that we add the definition
(not the declaration) to the list of deferred definitions to
emit. Fixes PR8864.

Thanks to Nick Lewycky for testing this	patch out



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@125157 91177308-0d34-0410-b5e6-96231b3b80d8