fix a minor bug I noticed while work with Jordy's patch for PR6101, in an input file like this:
fix a minor bug I noticed while work with Jordy's patch for PR6101,
in an input file like this:

# 42
int x;

we were emitting:

# <something>
 int x;

(with a space before the int) because we weren't clearing the leading 
whitespace flag properly after the \n from the directive was handled.


git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@101084 91177308-0d34-0410-b5e6-96231b3b80d8

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