Code quality: Fix header guards consistency

Adds `header_guards.sh` bash script, used in CI to validate future
changes. Can be run locally to fix invalid header guards.

modules/freetype/uwpdef.h

@@ -28,6 +28,11 @@
 /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
 /*************************************************************************/
 
+#ifndef UWPDEF_H
+#define UWPDEF_H
+
 // "generic" is a reserved keyword in C++/CX code
 // this avoids the errors in the variable name from Freetype code
 #define generic freetype_generic
+
+#endif // UWPDEF_H