Be more specific about libevent version
Be more specific about libevent version

Currently libcouchbase supports libevent >= 1.4
This means it won't compile on ubuntu 8.04

Change-Id: I1e1b9c9983d6b5d5dcc0afec77f4aee6d20306a5
Reviewed-on: http://review.couchbase.org/16644
Reviewed-by: Sergey Avseyev <87f6d5e4fd3644c3c20800cde7fd3ad1569370b3@gmail.com>
Tested-by: Sergey Avseyev <87f6d5e4fd3644c3c20800cde7fd3ad1569370b3@gmail.com>

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