BridJ: delay local ref deletion when calling java
BridJ: updated binaries for Darwin x86_64
BridJ: cleanup of some PointerIO caching nonsense (atomic references and string instance, notably)
BridJ: introduced LRU pointer cache (disable with -Dbridj.cache.pointers=false or BRIDJ_CACHE_POINTERS=0). Helps keep short-lived pointer garbage to a minimum for some use cases (see issue #440)