Allocate some memories in SPIRAM first.

Try to allocate some WiFi and LWIP memories in SPIRAM first. If
    failed, try to allocate in internal RAM then.

components/esp32/wifi_internal.c

@@ -0,0 +1,56 @@
+// Copyright 2015-2017 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "esp_attr.h"
+#include "esp_heap_caps.h"
+#include "sdkconfig.h"
+
+/*
+ If CONFIG_WIFI_LWIP_ALLOCATION_FROM_SPIRAM_FIRST is enabled. Prefer to allocate a chunk of memory in SPIRAM firstly.
+ If failed, try to allocate it in internal memory then.
+ */
+IRAM_ATTR void *wifi_malloc( size_t size )
+{
+#if CONFIG_WIFI_LWIP_ALLOCATION_FROM_SPIRAM_FIRST
+    return heap_caps_malloc_prefer(size, 2, MALLOC_CAP_DEFAULT|MALLOC_CAP_SPIRAM, MALLOC_CAP_DEFAULT|MALLOC_CAP_INTERNAL);
+#else
+    return malloc(size);
+#endif
+}
+
+/*
+ If CONFIG_WIFI_LWIP_ALLOCATION_FROM_SPIRAM_FIRST is enabled. Prefer to allocate a chunk of memory in SPIRAM firstly.
+ If failed, try to allocate it in internal memory then.
+ */
+IRAM_ATTR void *wifi_realloc( void *ptr, size_t size )
+{
+#if CONFIG_WIFI_LWIP_ALLOCATION_FROM_SPIRAM_FIRST
+    return heap_caps_realloc_prefer(ptr, size, 2, MALLOC_CAP_DEFAULT|MALLOC_CAP_SPIRAM, MALLOC_CAP_DEFAULT|MALLOC_CAP_INTERNAL);
+#else
+    return realloc(ptr, size);
+#endif
+}
+
+/*
+ If CONFIG_WIFI_LWIP_ALLOCATION_FROM_SPIRAM_FIRST is enabled. Prefer to allocate a chunk of memory in SPIRAM firstly.
+ If failed, try to allocate it in internal memory then.
+ */
+IRAM_ATTR void *wifi_calloc( size_t n, size_t size )
+{
+#if CONFIG_WIFI_LWIP_ALLOCATION_FROM_SPIRAM_FIRST
+    return heap_caps_calloc_prefer(n, size, 2, MALLOC_CAP_DEFAULT|MALLOC_CAP_SPIRAM, MALLOC_CAP_DEFAULT|MALLOC_CAP_INTERNAL);
+#else
+    return calloc(n, size);
+#endif
+}