yesno behaves differently in a corner case depending on ENABLE_NLS.
With an input of "y" followed by an EOF the input is considered to
be "no", because the last character is replaced with '\0'. It was
assumed that there is a newline, which doesn't have to be true.
If ENABLE_NLS is not set, getchar() reads y and accepts it as "yes",
looping through more getchar() calls until reaching newline or EOF.
* lib/yesno.c (yesno): Check for EOL before replacing.
* tests/test-yesno.sh: Add a test case (test along with gettext).