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>

tools/config.h.in

@@ -14,3 +14,6 @@
 
 /* Define to 1 if you have the <yajl/yajl_version.h> header file. */
 #undef HAVE_YAJL_YAJL_VERSION_H
+
+/* Define curses header to include. */
+#undef INCLUDE_CURSES_H