Canonize swift header files headers and footers

- Added missing ifdef guard in PointerIntEnum header
- Consistent naming convention for ifdef guards
- Consistent 'end namespace swift'
- Consistent single EOL at end of header files

include/swift/Basic/StringExtras.h

@@ -458,6 +458,7 @@ bool omitNeedlessWords(StringRef &baseName,
                        bool isProperty,
                        const InheritedNameSet *allPropertyNames,
                        StringScratchSpace &scratch);
-}
 
-#endif // LLVM_SWIFT_BASIC_STRINGEXTRAS_HPP
+} // end namespace swift
+
+#endif // SWIFT_BASIC_STRINGEXTRAS_H