Depend on async_nif.h
Use a set of {Session, Cursor} pairs ("passes") for calls into WiredTiger
to avoid a) opening a large number of Sessions or Cursors and b) avoid
reusing a Session/Cursor pair in more than one thread.  Each operation,
except folds, use the Session/Cursor pair corresponding to the scheduler
id (roughly "core") they are running on.  Each vnode instance will have
(count(schedulers) + count(active folds)) Session/Cursor pairs in use so
be sure to set session_max large enough when opening the connection to
WiredTiger.  This method will cause problems with scheduler threads going
to "sleep" so be sure to run schedmon to wake them up.
Remove check for other module.
Change from static linking to dynamic. Enable snappy and bzip2 compression.
Automatically load all WiredTiger extension shared libraries found in the priv dir at load time.
Add linker flags so that shared libraries are found relative to either the wterl layout or the Riak layout.
Whitespace
Add an RPATH to the extionsion shared libs so they can find objects in the priv/ directory at runtime
Merge remote-tracking branch 'origin/master' into gsb-async-nifs2

Conflicts:
	c_src/wterl.c
	src/riak_kv_wterl_backend.erl
	src/wterl.erl