feat: Make dcurl set the threadpool size of libtuv

In the initialization phase of dcurl,
the threadpool size is preset to the (maximum processor - 1)
with the new libtuv API uv_set_threadpool_size().
Then the threadpool would be initialized in the first call of dcurl_entry()
with the preset size.

Close #149.

src/pow_avx.c

@@ -607,6 +607,7 @@ static bool PoWAVX_Context_Initialize(ImplContext *impl_ctx)
         impl_ctx->bitmap = impl_ctx->bitmap << 1 | 0x1;
         uv_loop_init(&ctx[i].loop);
     }
+    uv_set_threadpool_size(nproc);
     impl_ctx->context = ctx;
     uv_mutex_init(&impl_ctx->lock);
     return true;

src/pow_c.c

@@ -371,6 +371,7 @@ static bool PoWC_Context_Initialize(ImplContext *impl_ctx)
         impl_ctx->bitmap = impl_ctx->bitmap << 1 | 0x1;
         uv_loop_init(&ctx[i].loop);
     }
+    uv_set_threadpool_size(nproc);
     impl_ctx->context = ctx;
     uv_mutex_init(&impl_ctx->lock);
     return true;

src/pow_sse.c

@@ -389,6 +389,7 @@ static bool PoWSSE_Context_Initialize(ImplContext *impl_ctx)
         impl_ctx->bitmap = impl_ctx->bitmap << 1 | 0x1;
         uv_loop_init(&ctx[i].loop);
     }
+    uv_set_threadpool_size(nproc);
     impl_ctx->context = ctx;
     uv_mutex_init(&impl_ctx->lock);
     return true;