Add more 'fall through' comments for switch cases

TODO: make sure these are actually meant to fall-through.

ctags/parsers/perl.c

@@ -138,9 +138,11 @@ SUB_DECL_SWITCH:
 				case ';':
 					if (!nparens)
 						return true;
+					/* fall through */
 				case '{':
 					if (!nparens)
 						return false;
+					/* fall through */
 				default:
 					if (attr) {
 						if (isIdentifier1(*cp)) {

ctags/parsers/r.c

@@ -142,6 +142,7 @@ static void createRTags (void)
 							break;
 						}
 					}
+					/* fall through */
 				case ' ':
 				case '\x009':
 					/* skip whitespace */