Track our own quickjs memory usage so that we can avoid expensive calls to JS_ComputeMemoryUsage.

git-svn-id: https://www.unprompted.com/svn/projects/tildefriends/trunk@3915 ed5197a5-7fde-0310-b194-c3ffbd925b24

src/mem.h

@@ -2,6 +2,8 @@
 
 #include <stddef.h>
 
+typedef struct JSMallocFunctions JSMallocFunctions;
+
 void tf_mem_replace_uv_allocator();
 size_t tf_mem_get_uv_malloc_size();
 
@@ -16,3 +18,6 @@ void tf_free(void* ptr);
 char* tf_strdup(const char* string);
 
 void* tf_resize_vec(void* ptr, size_t size);
+
+void tf_get_js_malloc_functions(JSMallocFunctions* out);
+size_t tf_mem_get_js_malloc_size();