Fix issue if generating error and call to MessageT() and thus ydb_message_t() returns CALLINAFTERXIT
Final Release Note
Description
At the current time, if ydb_message_t() returns a non-zero return code, MessageT() will panic. It should do some triage on the return code much like is done everywhere else we call the C SimpleAPI code from Go. This may be as simple as inserting a call to checkErrorReturn() and returning if it says to or something slightly more complex may be needed. Need to think on it a bit.
Draft Release Note
When an application is shutting down and some goroutine drives yottadb.Exit(), all other goroutines attempting to access the YottaDD SimpleAPI will get a YDB_ERR_CALLINAFTERXIT error. When a goroutine gets this failure from a TpST() call, MessageT() was called to provide the text - only MessageT() had an error introduced by merging #34 (closed) that made the error number positive BEFORE it did a check for YDB_ERR_CALLINAFTERXIT. This meant CALLINAFTERXIT was not recognized properly so MessageT() proceeded to call ydb_message_t() which failed with the same error code as the engine was shutdown. With this change, the CALLINAFTERXIT error is recognized early and handled correctly. Previously, the failure of ydb_message_t() would cause an erroneous panic().