Fix build error introduced in r334498
Fix build error introduced in r334498

Some gcc versions (circa 4.9) do not accept initializing Expected
objects containing a reference to a function from a function.

Change the Expected object to contain function pointers to work around
this.

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@334501 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb