CCBC-114 Lookup the plugin symbol in current executable image
CCBC-114 Lookup the plugin symbol in current executable image

The patch get back fallback with dlopen(NULL) which allows to search plugin
symbol in the main program. But if the fallback will return failure, the
create function will still use original error code.

Change-Id: Ie729d31d67ece5300e7c6c5a4568267380e8701d
Reviewed-on: http://review.couchbase.org/22265
Tested-by: Sergey Avseyev <87f6d5e4fd3644c3c20800cde7fd3ad1569370b3@gmail.com>
Reviewed-by: Michael Leib <e30901d366de547706d5a1f669f20de2b3deea40@yahoo.com>
Reviewed-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@gmail.com>

senthilkumaranb/libcouchbase,couchbase/libcouchbase,couchbase/libcouchbase,kojiromike/libcouchbase,avsej/libcouchbase,kojiromike/libcouchbase,couchbase/libcouchbase,PureSwift/libcouchbase,senthilkumaranb/libcouchbase,mody/libcouchbase,avsej/libcouchbase,mnunberg/libcouchbase,uvenum/libcouchbase,trondn/libcouchbase,signmotion/libcouchbase,kojiromike/libcouchbase,avsej/libcouchbase,senthilkumaranb/libcouchbase,maxim-ky/libcouchbase,uvenum/libcouchbase,senthilkumaranb/libcouchbase,kojiromike/libcouchbase,trondn/libcouchbase,uvenum/libcouchbase,couchbase/libcouchbase,avsej/libcouchbase,signmotion/libcouchbase,maxim-ky/libcouchbase,maxim-ky/libcouchbase,couchbase/libcouchbase,mody/libcouchbase,trondn/libcouchbase,PureSwift/libcouchbase,avsej/libcouchbase,avsej/libcouchbase,mnunberg/libcouchbase,couchbase/libcouchbase,mnunberg/libcouchbase,PureSwift/libcouchbase,avsej/libcouchbase,mnunberg/libcouchbase,trondn/libcouchbase,mnunberg/libcouchbase,signmotion/libcouchbase,uvenum/libcouchbase,maxim-ky/libcouchbase,mody/libcouchbase,mody/libcouchbase,couchbase/libcouchbase,PureSwift/libcouchbase,trondn/libcouchbase,uvenum/libcouchbase,signmotion/libcouchbase