patch 8.2.0035: saving and restoring called_emsg is clumsy

Problem:    Saving and restoring called_emsg is clumsy.
Solution:   Count the number of error messages.
diff --git a/src/globals.h b/src/globals.h
index 9ddb164..33082d5 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -226,7 +226,7 @@
 #endif
 EXTERN int	did_emsg_syntax;	    // did_emsg set because of a
 					    // syntax error
-EXTERN int	called_emsg;		    // always set by emsg()
+EXTERN int	called_emsg;		    // always incremented by emsg()
 EXTERN int	ex_exitval INIT(= 0);	    // exit value for ex mode
 EXTERN int	emsg_on_display INIT(= FALSE);	// there is an error message
 EXTERN int	rc_did_emsg INIT(= FALSE);  // vim_regcomp() called emsg()