core: switch from mousedown to drag functions

Due to crashes/freezes while moving some frames, one possible
reason could be that pfUI was using OnMouseDown and OnMouseUp
to run its frame-moving code. I have noticed better performance
when using the intended functions, OnDragStart and OnDragStop
to move frames.

This commit changes every occurrence of such functions and splits
drag and click into seperate functions where required.

modules/map.lua

@@ -39,6 +39,10 @@ pfUI:RegisterModule("map", "vanilla:tbc", function ()
 
     UIPanelWindows["WorldMapFrame"] = { area = "center" }
 
+    WorldMapFrame:SetMovable(true)
+    WorldMapFrame:EnableMouse(true)
+    WorldMapFrame:RegisterForDrag("LeftButton")
+
     WorldMapFrame:SetScript("OnShow", function()
       -- default events
       UpdateMicroButtons()
@@ -67,18 +71,15 @@ pfUI:RegisterModule("map", "vanilla:tbc", function ()
       SaveMovable(this, true)
     end)
 
-    WorldMapFrame:SetScript("OnMouseDown",function()
+    WorldMapFrame:SetScript("OnDragStart",function()
       WorldMapFrame:StartMoving()
     end)
 
-    WorldMapFrame:SetScript("OnMouseUp",function()
+    WorldMapFrame:SetScript("OnDragStop",function()
       WorldMapFrame:StopMovingOrSizing()
       SaveMovable(this, true)
     end)
 
-    WorldMapFrame:SetMovable(true)
-    WorldMapFrame:EnableMouse(true)
-
     WorldMapFrame:SetAlpha(alpha)
     WorldMapFrame:SetScale(scale)
     UpdateTooltipScale()