Silence some -Wimplicit-fallthrough by proper spelling

sql/sql_cache.cc

@@ -1757,7 +1757,7 @@ Query_cache::send_result_to_client(THD *thd, char *org_sql, uint query_length)
           sql++;
           continue;
         }
-        /* fall trough */
+        /* fall through */
       default:
         break;
       }

storage/maria/ma_search.c

@@ -747,11 +747,11 @@ void _ma_kpointer(register MARIA_HA *info, register uchar *buff, my_off_t pos)
   case 5: mi_int5store(buff,pos); break;
 #else
   case 7: *buff++=0;
-    /* fall trough */
+    /* fall through */
   case 6: *buff++=0;
-    /* fall trough */
+    /* fall through */
   case 5: *buff++=0;
-    /* fall trough */
+    /* fall through */
 #endif
   case 4: mi_int4store(buff,pos); break;
   case 3: mi_int3store(buff,pos); break;
@@ -883,13 +883,13 @@ void _ma_dpointer(MARIA_SHARE *share, uchar *buff, my_off_t pos)
   case 5: mi_int5store(buff,pos); break;
 #else
   case 8: *buff++=0;
-    /* fall trough */
+    /* fall through */
   case 7: *buff++=0;
-    /* fall trough */
+    /* fall through */
   case 6: *buff++=0;
-    /* fall trough */
+    /* fall through */
   case 5: *buff++=0;
-    /* fall trough */
+    /* fall through */
 #endif
   case 4: mi_int4store(buff,pos); break;
   case 3: mi_int3store(buff,pos); break;

storage/myisam/mi_search.c

@@ -608,11 +608,11 @@ void _mi_kpointer(register MI_INFO *info, register uchar *buff, my_off_t pos)
   case 5: mi_int5store(buff,pos); break;
 #else
   case 7: *buff++=0;
-    /* fall trough */
+    /* fall through */
   case 6: *buff++=0;
-    /* fall trough */
+    /* fall through */
   case 5: *buff++=0;
-    /* fall trough */
+    /* fall through */
 #endif
   case 4: mi_int4store(buff,pos); break;
   case 3: mi_int3store(buff,pos); break;
@@ -729,13 +729,13 @@ void _mi_dpointer(MI_INFO *info, uchar *buff, my_off_t pos)
   case 5: mi_int5store(buff,pos); break;
 #else
   case 8: *buff++=0;
-    /* fall trough */
+    /* fall through */
   case 7: *buff++=0;
-    /* fall trough */
+    /* fall through */
   case 6: *buff++=0;
-    /* fall trough */
+    /* fall through */
   case 5: *buff++=0;
-    /* fall trough */
+    /* fall through */
 #endif
   case 4: mi_int4store(buff,pos); break;
   case 3: mi_int3store(buff,pos); break;