Partially revert r91626. Materializing extra functions to determine whether

Partially revert r91626.  Materializing extra functions to determine whether
they're available_externally broke VMKit, which was relying on the fact that
functions would only be materialized when they were first called.  We'll have
to wait for http://llvm.org/PR5737 to really fix this.

I also added a test for one of the F->isDeclaration() calls which wasn't
covered by anything else in the test suite.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91943 91177308-0d34-0410-b5e6-96231b3b80d8