Don't compile the script so often during combat.

Don't compile the script so often during combat.

The UPDATE_SHAPESHIFT_FORM event fires far more often than it should
according to the documentation.  It will fire even when the player's
shapeshift form or stance doesn't change.  Modify the OvaleAura to catch
UPDATE_SHAPESHIFT_FORM(S) and verify that the stance actually changed
before raising a new event Ovale_UpdateShapeshiftForm that may caught by
other Ovale modules that care about stances.

This should fix the problem where the script was compiling very often
during combat for some classes.

git-svn-id: svn://svn.curseforge.net/wow/ovale/mainline/trunk@600 d5049fe3-3747-40f7-a4b5-f36d6801af5f