Fix #4: keyboard.disableFocus() not working.

Used undefined variable NO_WIDGET to clear keyboard focus.
Same error was made in mouse.lua.

core.lua

@@ -24,7 +24,6 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 ]]--
 
-local NO_WIDGET = function()end
 local BASE = (...):match("(.-)[^%.]+$")
 local group    = require(BASE .. 'group')
 local mouse    = require(BASE .. 'mouse')
@@ -83,6 +82,7 @@ local function registerDraw(id, f, ...)
 	if mouse.isHot(id) or keyboard.hasFocus(id) then
 		state = mouse.isActive(id) and 'active' or 'hot'
 	end
+	print(id, keyboard.hasFocus(id))
 	local rest = save_pack(...)
 	draw_items.n = draw_items.n + 1
 	draw_items[draw_items.n] = function()

keyboard.lua

@@ -26,6 +26,7 @@ THE SOFTWARE.
 
 local key,code = nil, -1
 local focus, lastwidget
+local NO_WIDGET = {}
 
 local cycle = {
 	-- binding = {key = key, modifier1, modifier2, ...} XXX: modifiers are OR-ed!

mouse.lua

@@ -29,6 +29,7 @@ local _M -- holds the module. needed to make widgetHit overridable
 local x,y = 0,0
 local down = false
 local hot, active = nil, nil
+local NO_WIDGET = {}
 
 local function widgetHit(mouse, pos, size)
 	return mouse[1] >= pos[1] and mouse[1] <= pos[1] + size[1] and