patch 8.2.3959: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more errors to errors.h.
diff --git a/src/evalvars.c b/src/evalvars.c
index 4ddd215..03ed5c1 100644
--- a/src/evalvars.c
+++ b/src/evalvars.c
@@ -626,7 +626,7 @@
 	*p = NUL;
 	if (!script_get && vim_islower(*marker))
 	{
-	    emsg(_("E221: Marker cannot start with lower case letter"));
+	    emsg(_(e_marker_cannot_start_with_lower_case_letter));
 	    return NULL;
 	}
     }