Synchronize globally-cached code completion results with the results

provided when the optimization is disabled. In particular, split
the completion context CCC_Other into two contexts: CCC_Other, which
means that it's an undisclosed context for which any other results are
unwelcome, and CCC_Recovery, which is used in recovery cases.

Since we're now using the completion context within the completion
results builder, make sure that it's always set to something.

Fixes <rdar://problem/8470644>.

llvm-svn: 114704