Clear AFK on wake only while it is still set

/afk toggles. The overlay sent it on every click and key press, so when
the client or the server had already cleared AFK it set it again. Check
ClassicAPI's IsChatAFK first. It follows the client's /afk state at
once, where UnitIsAFK waits for the server's flag update.

modules/afkcam.lua

@@ -29,20 +29,20 @@ pfUI:RegisterModule("afkcam", function ()
   overlay:SetFrameStrata("DIALOG")
   overlay:SetAllPoints(WorldFrame)
 
-  overlay:SetScript("OnMouseUp",function()
-    SendChatMessage("","AFK")
-    this._parent:stop()
-  end)
+  -- /afk toggles, so send it only while AFK is still set: once the client
+  -- or the server has cleared it, /afk would set it again
+  local function Wake()
+    if IsChatAFK() then SendChatMessage("", "AFK") end
+    afkcam:stop()
+  end
+  overlay:SetScript("OnMouseUp", Wake)
   overlay:SetScript("OnShow", function()
     this:EnableKeyboard(true)
   end)
   overlay:SetScript("OnHide", function()
     this:EnableKeyboard(false)
   end)
-  overlay:SetScript("OnKeyUp",function()
-    SendChatMessage("","AFK")
-    this._parent:stop()
-  end)
+  overlay:SetScript("OnKeyUp", Wake)
   overlay:Hide()
 
   local chat = CreateFrame("ScrollingMessageFrame", "pfAFKCamChat", overlay)
@@ -82,7 +82,6 @@ pfUI:RegisterModule("afkcam", function ()
   end)
   overlay.chat = chat
 
-  overlay._parent = afkcam
   afkcam.overlay = overlay
 
   local clock = CreateFrame("Frame", "pfAFKClock", overlay)