Sending messages
This function enables users to send a message from within a user primitive and retrieve the result. 
U_32 EsSendMessage(EsVMContext vmContext, EsObject * returnObject, EsObject receiver, EsObject selector, U_32 argumentCount, ...) 
Calls back into the VA Smalltalk interpreter by sending a message. returnObject is a pointer to an EsObject where the return value of the message is placed. argumentCount can be from 0 to 255. 
Error cases: Returns an EsPrimErr code. 
Side effects: This operation can cause a garbage collection.  
Last modified date: 01/29/2015