ggml : various fixes (#1450)

- `ggml_rope()`
- `ggml_diag_mask_inf()` multi-threaded
- compatibility with scratch buffers

ggml.h

@@ -340,7 +340,7 @@ extern "C" {
 
     // n-dimensional tensor
     struct ggml_tensor {
-        enum ggml_type type;
+        enum ggml_type    type;
         enum ggml_backend backend;
 
         int     n_dims;
@@ -372,7 +372,7 @@ extern "C" {
 
         char name[32];
 
-        char padding[9]; // TODO: remove and add padding to name?
+        char padding[16];
     };
 
     // computation graph