Added stix_shallowcopy().

added some code for bigint operations

stix/lib/stix.h

@@ -794,6 +794,11 @@ STIX_EXPORT void stix_gc (
 	stix_t* stix
 );
 
+STIX_EXPORT stix_oow_t stix_getpayloadbytes (
+	stix_t*    stix,
+	stix_oop_t oop
+);
+
 /**
  * The stix_instantiate() function creates a new object of the class 
  * \a _class. The size of the fixed part is taken from the information
@@ -810,6 +815,11 @@ STIX_EXPORT stix_oop_t stix_instantiate (
 	stix_oow_t       vlen
 );
 
+STIX_EXPORT stix_oop_t stix_shallowcopy (
+	stix_t*          stix,
+	stix_oop_t       oop
+);
+
 /**
  * The stix_ignite() function creates key initial objects.
  */