patch 8.2.3750: error messages are everywhere

Problem:    Error messages are everywhere.
Solution:   Move more error messages to errors.h and adjust the names.
diff --git a/src/term.c b/src/term.c
index a8819a3..f74b18a 100644
--- a/src/term.c
+++ b/src/term.c
@@ -6021,7 +6021,7 @@
 	    if (STRNICMP(src, "<SID>", 5) == 0)
 	    {
 		if (current_sctx.sc_sid <= 0)
-		    emsg(_(e_usingsid));
+		    emsg(_(e_using_sid_not_in_script_context));
 		else
 		{
 		    src += 5;