Feature: Use arena-allocation for memory handling

Arena allocation make deallocation of nested structed MUCH faster, and
improves the spatial locality of allocations. It makes no sense to
deallocate only parts of a JSON structure so arenas are a good fit here.

include/parse.h

@@ -4,8 +4,9 @@
 
 #include "json_value.h"
 
+#include "arena.h"
 #include <stdio.h> // FILE*
 
-struct json_value parse_json_value(FILE* fp);
+struct json_value parse_json_value(FILE* fp, arena_t* arena);
 
 #endif