Added a test stub.
Added some test names.
LruCacheTest.Empty
LruCacheTest.LookUpUnknownKey
LruCacheTest.FillUpToCapacity
Began implementing.
Fixed some build errors.
Implemented erase_Locked.
Brain-dead LookUp implementation.
Implemented NewLruCache.
LruCacheTest.InsertNilValue
Check for nil.
LruCacheTest.ExpiresLeastRecentlyUsed
LruCacheTest.Overwrite
Refactored.
Trim when necessary.
Promote on lookup.
Check invariants when unlocking.
LruCacheTest.SafeForConcurrentAccess
Fixed a deadlock.