Move a method from IdentifierTable.h out of line and remove the SmallString include.

Fix all the transitive include users.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@149783 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/StaticAnalyzer/Checkers/UnixAPIChecker.cpp b/lib/StaticAnalyzer/Checkers/UnixAPIChecker.cpp
index 375dc82..f188d2d 100644
--- a/lib/StaticAnalyzer/Checkers/UnixAPIChecker.cpp
+++ b/lib/StaticAnalyzer/Checkers/UnixAPIChecker.cpp
@@ -19,6 +19,7 @@
 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
 #include "clang/Basic/TargetInfo.h"
 #include "llvm/ADT/Optional.h"
+#include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringSwitch.h"
 #include <fcntl.h>