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/Unicode.h

@@ -83,8 +83,7 @@ unsigned extractFirstUnicodeScalar(StringRef S);
 /// Returns the number of code units in UTF16 representation
 uint64_t getUTF16Length(StringRef Str);
 
-} // namespace unicode
-} // namespace swift
-
-#endif
+} // end namespace unicode
+} // end namespace swift
 
+#endif // SWIFT_BASIC_UNICODE_H