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/map.c b/src/map.c
index a958803..311f4da 100644
--- a/src/map.c
+++ b/src/map.c
@@ -603,12 +603,11 @@
 			    && STRNCMP(mp->m_keys, keys, (size_t)len) == 0)
 		    {
 			if (abbrev)
-			    semsg(_(
-			    "E224: global abbreviation already exists for %s"),
+			    semsg(
+			       _(e_global_abbreviation_already_exists_for_str),
 				    mp->m_keys);
 			else
-			    semsg(_(
-				 "E225: global mapping already exists for %s"),
+			    semsg(_(e_global_mapping_already_exists_for_str),
 				    mp->m_keys);
 			retval = 5;
 			goto theend;
@@ -741,12 +740,11 @@
 			    else if (unique)
 			    {
 				if (abbrev)
-				    semsg(_(
-				   "E226: abbreviation already exists for %s"),
+				    semsg(
+				      _(e_abbreviation_already_exists_for_str),
 					    p);
 				else
-				    semsg(_(
-					"E227: mapping already exists for %s"),
+				    semsg(_(e_mapping_already_exists_for_str),
 					    p);
 				retval = 5;
 				goto theend;
@@ -1855,7 +1853,7 @@
 			c1 = 't';
 			break;
 		    default:
-			iemsg(_("E228: makemap: Illegal mode"));
+			iemsg(_(e_makemap_illegal_mode));
 			return FAIL;
 		}
 		do	// do this twice if c2 is set, 3 times with c3