patch 8.2.4010: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more error messages to errors.h.
diff --git a/src/diff.c b/src/diff.c
index fa2ab41..5a98196 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -1096,7 +1096,7 @@
     if (!ok)
     {
 	if (io_error)
-	    emsg(_("E810: Cannot read or write temp files"));
+	    emsg(_(e_cannot_read_or_write_temp_files));
 	emsg(_(e_cannot_create_diffs));
 	diff_a_works = MAYBE;
 #if defined(MSWIN)
@@ -1337,7 +1337,7 @@
 
     // Only continue if the output file was created.
     if (mch_stat((char *)tmp_new, &st) < 0 || st.st_size == 0)
-	emsg(_("E816: Cannot read patch output"));
+	emsg(_(e_cannot_read_patch_output));
     else
     {
 	if (curbuf->b_fname != NULL)