API C MapBar.GetCurrentValue

__NOTOC__
Returns current progress towards unlocking the next phase of the current map.
 currentValue = C_MapBar.GetCurrentValue()
==Returns==
; currentValue : Number - current progress towards unlocking the next phase of the current map; nil if the current map does not use the map bar.
==Details==
* The returned values are in arbitrary units; returns the value required to trigger the next phase.
==Patch changes==
*