add json_tokener_parse_verbose, and return NULL on parser errors

git-svn-id: http://svn.metaparadigm.com/svn/json-c/trunk@62 327403b1-1117-474d-bef2-5cb71233fd97

bits.h

@@ -22,6 +22,7 @@
 
 #define hexdigit(x) (((x) <= '9') ? (x) - '0' : ((x) & 7) + 9)
 #define error_ptr(error) ((void*)error)
-#define is_error(ptr) ((unsigned long)ptr > (unsigned long)-4000L)
+#define error_description(error)  (json_tokener_errors[error])
+#define is_error(ptr) (ptr == NULL)
 
 #endif