patch 8.2.3977: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more error messages to errors.h.
diff --git a/src/memline.c b/src/memline.c
index a072746..a4485c8 100644
--- a/src/memline.c
+++ b/src/memline.c
@@ -327,7 +327,7 @@
 	goto error;
     if (hp->bh_bnum != 0)
     {
-	iemsg(_("E298: Didn't get block nr 0?"));
+	iemsg(_(e_didnt_get_block_nr_zero));
 	goto error;
     }
     b0p = (ZERO_BL *)(hp->bh_data);
@@ -377,7 +377,7 @@
 	goto error;
     if (hp->bh_bnum != 1)
     {
-	iemsg(_("E298: Didn't get block nr 1?"));
+	iemsg(_(e_didnt_get_block_nr_one));
 	goto error;
     }
     pp = (PTR_BL *)(hp->bh_data);
@@ -395,7 +395,7 @@
 	goto error;
     if (hp->bh_bnum != 2)
     {
-	iemsg(_("E298: Didn't get block nr 2?"));
+	iemsg(_(e_didnt_get_block_nr_two));
 	goto error;
     }