patch 8.1.1318: code for text changes is in a "misc" file

Problem:    Code for text changes is in a "misc" file.
Solution:   Move the code to change.c.
diff --git a/src/memline.c b/src/memline.c
index 1ef7ecf..812d10d 100644
--- a/src/memline.c
+++ b/src/memline.c
@@ -1637,7 +1637,7 @@
 	 * empty.  Don't set the modified flag then. */
 	if (!(curbuf->b_ml.ml_line_count == 2 && *ml_get(1) == NUL))
 	{
-	    changed_int();
+	    changed_internal();
 	    ++CHANGEDTICK(curbuf);
 	}
     }
@@ -1651,7 +1651,7 @@
 	    vim_free(p);
 	    if (i != 0)
 	    {
-		changed_int();
+		changed_internal();
 		++CHANGEDTICK(curbuf);
 		break;
 	    }