Change OvaleSpellBook:IsUsableSpell() to allow checking unlearned spells.

diff --git a/OvaleSpellBook.lua b/OvaleSpellBook.lua
index 0bd013a..78a2c42 100644
--- a/OvaleSpellBook.lua
+++ b/OvaleSpellBook.lua
@@ -1,7 +1,7 @@
 --[[--------------------------------------------------------------------
     Ovale Spell Priority
     Copyright (C) 2012 Sidoine
-    Copyright (C) 2012, 2013 Johnny C. Lam
+    Copyright (C) 2012, 2013, 2014 Johnny C. Lam

     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License in the LICENSE
@@ -33,6 +33,7 @@ local API_GetSpellLink = GetSpellLink
 local API_GetSpellTabInfo = GetSpellTabInfo
 local API_GetTalentInfo = GetTalentInfo
 local API_HasPetSpells = HasPetSpells
+local API_IsSpellOverlayed = IsSpellOverlayed
 local API_IsUsableSpell = IsUsableSpell
 local BOOKTYPE_PET = BOOKTYPE_PET
 local BOOKTYPE_SPELL = BOOKTYPE_SPELL
@@ -254,15 +255,14 @@ function OvaleSpellBook:IsKnownTalent(talentId)
 end

 -- Returns true if the given spell ID is usable.  A spell is *not* usable if:
---     The player hasn't learned the spell.
 --     The player lacks required mana or reagents.
 --     Reactive conditions haven't been met.
+-- XXX Use IsSpellOverlayed() to catch instances where a spell becomes usable due
+-- XXX to a proc but the proc replaces the spell in the spellbook, e.g.,
+-- XXX "Aimed Shot" --> "Aimed Shot!".
 function OvaleSpellBook:IsUsableSpell(spellId)
 	local name = self:GetSpellName(spellId)
-	if name then
-		return API_IsUsableSpell(self:GetSpellName(spellId))
-	end
-	return false
+	return API_IsUsableSpell(name) or API_IsSpellOverlayed(spellId)
 end

 -- Print out the list of active glyphs in alphabetical order.