If something already instantiated is reinstantiated as an explicit definition, keep the latter.
If something already instantiated is reinstantiated as an explicit definition,
keep the latter.

No test. This was noticed when poking around something else with GDB. I'm not
able to figure out a testcase that would break due to this bug. Sorry.


git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@153992 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang