ggml : GPU-accelerated token generation (#1412)

* CUDA kernel for q4_0 dequant. + mat. vec. mult.

* Added q4_1 via template

* Added missing __syncthreads();

* --gpu_layers -> --gpu-layers

* Shorter dequantize_mul_mat_vec line

* q5_0 dequantize_mul_mat kernel

* More readable dequantize_mul_mat_vec logic

* dequantize_mul_mat_vec kernels for q5_1, q8_0, f16

* llama : offload "output" tensor to GPU too + coding style fixes

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Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

ggml.c

@@ -3882,6 +3882,7 @@ struct ggml_tensor * ggml_new_tensor_impl(
 
     *result = (struct ggml_tensor) {
         /*.type         =*/ type,
+        /*.backend      =*/ GGML_BACKEND_CPU,
         /*.n_dims       =*/ n_dims,
         /*.ne           =*/ { 1, 1, 1, 1 },
         /*.nb           =*/ { 0, 0, 0, 0 },