patch 8.2.4005: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more error messages to errors.h.
diff --git a/src/ex_cmds2.c b/src/ex_cmds2.c
index b118c2d..d2b45ab 100644
--- a/src/ex_cmds2.c
+++ b/src/ex_cmds2.c
@@ -761,7 +761,7 @@
 
 	    sprintf((char *)buf, "compiler/%s.vim", eap->arg);
 	    if (source_runtime(buf, DIP_ALL) == FAIL)
-		semsg(_("E666: compiler not supported: %s"), eap->arg);
+		semsg(_(e_compiler_not_supported_str), eap->arg);
 	    vim_free(buf);
 
 	    do_cmdline_cmd((char_u *)":delcommand CompilerSet");