Support Android compatibility (revised)
Support Android compatibility (revised)

- Replace spin lock by mutex.
- Get rid of assert calls.
- Use memalign instead of posix_memalign (not supported in Android).

sushmaad/forestdb,sushmaad/forestdb,couchbase/forestdb,uvenum/forestdb,joliss/forestdb,couchbase/forestdb,seem-sky/forestdb,jinxuan/forestdb,nvoron23/forestdb,nvoron23/forestdb,uvenum/forestdb,hisundar/forestdb,zhaog/forestdb,hisundar/forestdb,wurikiji/forestdb,joliss/forestdb,jinxuan/forestdb,yyangpan/forestdb,zhaog/forestdb,wurikiji/forestdb,yyangpan/forestdb,seem-sky/forestdb