EXTERN.h - Add whitespace to comment to make more readable

Makes it a bit more clear that this is documenting two things.

Author: demerphq

EXTERN.h

@@ -9,10 +9,11 @@
  */
 
 /*
- * EXT  designates a global var which is defined in perl.h
- * dEXT designates a global var which is defined in another
- *      file, so we can't count on finding it in perl.h
- *      (this practice should be avoided).
+ * EXT:  designates a global var which is defined in perl.h
+ *
+ * dEXT: designates a global var which is defined in another
+ *       file, so we can't count on finding it in perl.h
+ *       (this practice should be avoided).
  */
 #undef EXT
 #undef dEXT