Use OvalePool to reduce memory usage in OvaleAura.

Use OvalePool to reduce memory usage in OvaleAura.

Create a pool of auras that are used (and reused) when recording the auras
present on a unit.  This bounds the memory used by OvaleAura instead of
letting the garbage collector reclaim unused memory.

Don't pass around tables between modules; this decreases linkage between
modules by not exposing internal data structures and improves overall
encapsulation.

git-svn-id: svn://svn.curseforge.net/wow/ovale/mainline/trunk@777 d5049fe3-3747-40f7-a4b5-f36d6801af5f