Use ClassicAPI animation groups for fades and pulses

Replace hand-rolled OnUpdate alpha loops with engine animation groups:
unit frame aggro/combat glow, tracking icon pulse, new-mail blink,
castbar fade-out, autohide, XP/rep bar fade, info box timeout and the
unlock-mode scale label. Timing no longer depends on framerate, and the
always-running glow driver and tracking OnUpdate are gone.

The XP bar tracks hover through OnEnter/OnLeave instead of MouseIsOver,
so a fade can't restart under the cursor.

api/api.lua

@@ -1555,11 +1555,20 @@ function pfUI.api.EnableAutohide(frame, timeout, combat)
   frame.hover.parent = frame
   frame.hover:Show()
 
+  if not frame.hover.fade then
+    frame.hover.fade = frame:CreateAnimationGroup()
+    local fade = frame.hover.fade:CreateAnimation("Alpha")
+    fade:SetChange(-1)
+    fade:SetDuration(1)
+    frame.hover.fade:SetScript("OnFinished", function() frame:SetAlpha(0) end)
+  end
+
   if combat then
     frame.hover:RegisterEvent("PLAYER_REGEN_ENABLED")
     frame.hover:RegisterEvent("PLAYER_REGEN_DISABLED")
     frame.hover:SetScript("OnEvent", function()
       if event == "PLAYER_REGEN_DISABLED" then
+        this.fade:Stop()
         this.parent:SetAlpha(1)
         this.activeTo = "keep"
       elseif event == "PLAYER_REGEN_ENABLED" then
@@ -1577,11 +1586,11 @@ function pfUI.api.EnableAutohide(frame, timeout, combat)
 
     if MouseIsOver(this, 10, -10, -10, 10) then
       this.activeTo = GetTime() + timeout
+      this.fade:Stop()
       this.parent:SetAlpha(1)
     elseif this.activeTo then
-      if this.activeTo < GetTime() and this.parent:GetAlpha() > 0 then
-        local fps = (60 / math.max(GetFramerate(), 1))
-        this.parent:SetAlpha(this.parent:GetAlpha() - 0.05*fps)
+      if this.activeTo < GetTime() and this.parent:GetAlpha() > 0 and not this.fade:IsPlaying() then
+        this.fade:Play()
       end
     else
       this.activeTo = GetTime() + timeout
@@ -1598,6 +1607,7 @@ function pfUI.api.DisableAutohide(frame)
   frame.hover:SetScript("OnEvent", nil)
   frame.hover:SetScript("OnUpdate", nil)
   frame.hover:Hide()
+  frame.hover.fade:Stop()
   frame:SetAlpha(1)
 end