bug#21677: Guile-NCurses 1.6 test failure with ncurses 6.0

[Ludovic Courtès]

When compiled with NCurses 6.0, guile-ncurses 1.6 has one test failure:

--8<---------------cut here---------------start------------->8---
FAIL: curses_034_util.test

[...]

============================================================================
Testsuite summary for GNU Guile-Ncurses 1.6
============================================================================
# TOTAL: 71
# PASS:  70
# SKIP:  0
# XFAIL: 0
# FAIL:  1
# XPASS: 0
# ERROR: 0
--8<---------------cut here---------------end--------------->8---

This was fine with NCurses 5.0.

Ludo’.