heap: Add C++ header guards to heap headers

Closes https://github.com/espressif/esp-idf/issues/1195

components/heap/include/esp_heap_caps_init.h

@@ -17,6 +17,10 @@
 #include "esp_heap_caps.h"
 #include "soc/soc_memory_layout.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /**
  * @brief Initialize the capability-aware heap allocator.
  *
@@ -82,5 +86,6 @@ esp_err_t heap_caps_add_region(intptr_t start, intptr_t end);
 esp_err_t heap_caps_add_region_with_caps(const uint32_t caps[], intptr_t start, intptr_t end);
 
 
-
-
+#ifdef __cplusplus
+}
+#endif