ncurses-5.9 compilation warning

[Ilya Gordeev]

Compiling ncurses-5.9 by gcc-4.9.2 I'v got this message:
ncurses/base/lib_getch.c:177:19: warning: array subscript is below array bounds 
[-Warray-bounds]

It's because sometimes "head" may be equal to -1 but it is not handled before 
accessing to sp->_fifo[head] in fifo_pull()
For example, fifo_pull() may be called in nc_wgetch() within condition block "if (head == -1 
&& ...)"


Ilya Gordeev.