BTreeMap: do not check released locks every time, speedups some operations.
BTreeMap: do not check released locks every time, speedups some operations.

ringoluo/mapdb,sumit784/mapdb,SleimanJneidi/mapdb,ffjiao/mapdb,jankotek/MapDB,mebigfatguy/mapdb,jankotek/mapdb,morfeo8marc/mapdb,binarytemple/mapdb,codeaudit/mapdb,pettermahlen/mapdb,olupas/MapDB,mebigfatguy/mapdb,olupas/MapDB,cocosli/mapdb,lamfire/mapdb,hangum/mapdb,jankotek/MapDB,jankotek/mapdb