Remove widget values.

* WWidget no longer stores a value independent of its connected controls.
* Make a connection explicitly the display value. For legacy reasons this is the
  last connection with connectValueToWidget.
* Update all WWidget descendents to use the connected display value when
  painting.
* Push buttons update the left or right connected control for push-button
  behavior or toggling.

This allows WPushButton to toggle a multi-state button on left and right
click. This was previously impossible.
Assert ControlWidgetConnection::m_pControl is non-NULL.
Rename ControlWidgetConnection methods to be more clear.
Add comment to left-click push button handling.
Rename methods for getting and setting connected control parameters to be more clear.
Delete widget connections when the widget is deleted.
Update xwax to 1.4, no major changes.
Don't allow hotcues to be used in absolute mode.
Make it more explicit that vinyl hotcueing mode does get used.
If the user causes a sync while absolute mode is on, disable it.
Fix reverse mode not working with vinyl control.
change some logic to allow functionality with constant mode, not just relative
fix vinyl reverse mode logic
Inline the update_monitor functions since they get called for every sample.
Style misc.
Eliminate Needle Skip Prevention Mode.  It never worked.
Wrong destructor :-/.
Rename reset() to resetControl().
Add parentheses for clarity.
Merge pull request #146 from rryan/basewidget

Remove widget values.
Revert "Build a libmixxx.a and link it into mixxx and mixxx-test."

This reverts commit 63464477257b698ae475cfbff40a74428a8279ec.

Conflicts:
	src/SConscript
Merge pull request #148 from ywwg/vinyl-abs-fix-2

Updates and fixes to vinyl control