autoconf: add check for curses library

autoconf: add check for curses library

Check for a curses compatible library (curses or ncurses basically).
One of those is needed to compile Xen tools (gtraceview and xentop).

Modify Makefiles/sources to use configure output (fetch CURSES_LIBS
from tools/Tools.mk and header to include from tools/config.h)

Signed-off-by: Roger Pau Monne <roger.pau@entel.upc.edu>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>