Initial implementation of floats in Expr::tryEvaluate; this doesn't  implement some things, like unary operators and casts, but it's enough to fix PR2703 as filed.
Initial implementation of floats in Expr::tryEvaluate; this doesn't 
implement some things, like unary operators and casts, but it's enough
to fix PR2703 as filed.



git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@55155 91177308-0d34-0410-b5e6-96231b3b80d8

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