Fix undefined behavior that is caused by not always initializing a bool.
Fix undefined behavior that is caused by not always initializing a bool.

The fix in r310994 is incomplete, as moveFromAndCancel can set the
pointer without initializing OldIsSpeculativelyEvaluating.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@311070 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 5f96802aec23e60d2fc34bb977d97012cd15c4fe)

apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang