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/EncodedSequence.h

@@ -371,4 +371,4 @@ public:
 
 } // end namespace swift
 
-#endif
+#endif // SWIFT_BASIC_ENCODEDSEQUENCE_H