Add wrappers for malloc/realloc/free. See #43.

parser.y

@@ -2,6 +2,9 @@
 #include <stdio.h>
 #include <string.h>
 #include "compile.h"
+#include "jv_alloc.h"
+#define YYMALLOC jv_mem_alloc
+#define YYFREE jv_mem_free
 
 struct lexer_param;