Prevented 0-length string bug in vui_debugf
Prevented 0-length string bug in vui_debugf

vui_debugf was being called before the first call to initscr(), so COLS
was still 0 at the time.  It then called vsnprintf with a max length of 0
and printed the resulting invalid string.

Also made vui_debugf allocate max(COLS, 256) bytes for its output string.

electrodude/vui