Use fallthrough statement attribute

lib/roken/fnmatch.c

@@ -129,6 +129,7 @@ rk_fnmatch(const char *pattern, const char *string, int flags)
 					--pattern;
 				}
 			}
+                        fallthrough
 			/* FALLTHROUGH */
 		default:
 			if (c != *string++)

lib/roken/getuserinfo.c

@@ -136,7 +136,8 @@ roken_get_homedir(char *home, size_t homesz)
         }
         return home;
     }
-    /* Fallthru to return NULL */
+    fallthrough
+    /* FALLTHROUGH */
 #else
 #ifdef HAVE_GETPWNAM_R
     size_t buflen = 2048;

lib/roken/snprintf.c

@@ -515,6 +515,7 @@ xyzprintf (struct snprintf_state *state, const char *char_format, va_list ap)
 	    }
 	    case '\0' :
 		--format;
+                fallthrough
 		/* FALLTHROUGH */
 	    case '%' :
 		(*state->append_char)(state, c);

lib/roken/strftime.c

@@ -377,6 +377,7 @@ strftime (char *buf, size_t maxsize, const char *format,
 		break;
 	    case '\0' :
 		--format;
+                fallthrough
 		/* FALLTHROUGH */
 	    case '%' :
 		ret = snprintf (buf, maxsize - n,

lib/roken/strptime.c

@@ -424,6 +424,7 @@ strptime (const char *buf, const char *format, struct tm *timeptr)
 		abort ();
 	    case '\0' :
 		--format;
+                fallthrough
 		/* FALLTHROUGH */
 	    case '%' :
 		if (*buf == '%')