Suppress compiler warnings

dlib/general_hash/murmur_hash3.h

@@ -214,9 +214,9 @@ namespace dlib
         switch(len & 3)
         {
             case 3: k1 ^= tail[2] << 16;
-                    // fall through
+                    [[fallthrough]]; // fall through
             case 2: k1 ^= tail[1] << 8;
-                    // fall through
+                    [[fallthrough]]; // fall through
             case 1: k1 ^= tail[0];
                     k1 *= c1; k1 = DLIB_ROTL32(k1,15); k1 *= c2; h1 ^= k1;
         };
@@ -386,24 +386,24 @@ namespace dlib
 
         switch(len & 15)
         {
-            case 15: k2 ^= uint64(tail[14]) << 48; // fall through
-            case 14: k2 ^= uint64(tail[13]) << 40; // fall through
-            case 13: k2 ^= uint64(tail[12]) << 32; // fall through
-            case 12: k2 ^= uint64(tail[11]) << 24; // fall through
-            case 11: k2 ^= uint64(tail[10]) << 16; // fall through
-            case 10: k2 ^= uint64(tail[ 9]) << 8; // fall through
+            case 15: k2 ^= uint64(tail[14]) << 48; [[fallthrough]]; // fall through
+            case 14: k2 ^= uint64(tail[13]) << 40; [[fallthrough]]; // fall through
+            case 13: k2 ^= uint64(tail[12]) << 32; [[fallthrough]]; // fall through
+            case 12: k2 ^= uint64(tail[11]) << 24; [[fallthrough]]; // fall through
+            case 11: k2 ^= uint64(tail[10]) << 16; [[fallthrough]]; // fall through
+            case 10: k2 ^= uint64(tail[ 9]) << 8; [[fallthrough]]; // fall through
             case  9: k2 ^= uint64(tail[ 8]) << 0;
-                     k2 *= c2; k2  = DLIB_ROTL64(k2,33); k2 *= c1; h2 ^= k2; // fall through
-
-            case  8: k1 ^= uint64(tail[ 7]) << 56; // fall through
-            case  7: k1 ^= uint64(tail[ 6]) << 48; // fall through
-            case  6: k1 ^= uint64(tail[ 5]) << 40; // fall through
-            case  5: k1 ^= uint64(tail[ 4]) << 32; // fall through
-            case  4: k1 ^= uint64(tail[ 3]) << 24; // fall through
-            case  3: k1 ^= uint64(tail[ 2]) << 16; // fall through
-            case  2: k1 ^= uint64(tail[ 1]) << 8; // fall through
+                     k2 *= c2; k2  = DLIB_ROTL64(k2,33); k2 *= c1; h2 ^= k2; [[fallthrough]]; // fall through
+
+            case  8: k1 ^= uint64(tail[ 7]) << 56; [[fallthrough]]; // fall through
+            case  7: k1 ^= uint64(tail[ 6]) << 48; [[fallthrough]]; // fall through
+            case  6: k1 ^= uint64(tail[ 5]) << 40; [[fallthrough]]; // fall through
+            case  5: k1 ^= uint64(tail[ 4]) << 32; [[fallthrough]]; // fall through
+            case  4: k1 ^= uint64(tail[ 3]) << 24; [[fallthrough]]; // fall through
+            case  3: k1 ^= uint64(tail[ 2]) << 16; [[fallthrough]]; // fall through
+            case  2: k1 ^= uint64(tail[ 1]) << 8; [[fallthrough]]; // fall through
             case  1: k1 ^= uint64(tail[ 0]) << 0;
-                     k1 *= c1; k1  = DLIB_ROTL64(k1,31); k1 *= c2; h1 ^= k1; // fall through
+                     k1 *= c1; k1  = DLIB_ROTL64(k1,31); k1 *= c2; h1 ^= k1; 
         };
 
         //----------