updated for version 7.4.261
Problem:    When updating the window involves a regexp pattern, an interactive
            substitute to replace a "\n" with a line break fails. (Ingo
            Karkat)
Solution:   Set reg_line_lbr in vim_regsub() and vim_regsub_multi().
diff --git a/src/regexp.c b/src/regexp.c
index 2c364b3..2023714 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -7381,6 +7381,7 @@
     reg_mmatch = NULL;
     reg_maxline = 0;
     reg_buf = curbuf;
+    reg_line_lbr = TRUE;
     return vim_regsub_both(source, dest, copy, magic, backslash);
 }
 #endif
@@ -7400,6 +7401,7 @@
     reg_buf = curbuf;		/* always works on the current buffer! */
     reg_firstlnum = lnum;
     reg_maxline = curbuf->b_ml.ml_line_count - lnum;
+    reg_line_lbr = FALSE;
     return vim_regsub_both(source, dest, copy, magic, backslash);
 }