Changed error code reported when file not found for G65 macro or named O-sub calls from 39 to 84.

Removed IDLE state requirement for executing G65 macros, an error will no longer be returned and the macro will be run.
Added event handler for outputting welcome message on "native" USB connect for drivers that provides the linestate changed event.

errors.c

@@ -104,6 +104,7 @@ PROGMEM static const status_detail_t status_detail[] = {
     { Status_FlowControlStackOverflow, "Stack overflow while executing flow statement." },
     { Status_FlowControlOutOfMemory, "Out of memory while executing flow statement." },
 #endif
+    { Status_FileOpenFailed, "Could not open file." },
     { Status_UserException, "User defined error occured." }
 #endif // NO_SETTINGS_DESCRIPTIONS
 };