gh-148: fix a failing small_alloc.test on 32 bit platforms.
gh-148: fix a failing small_alloc.test on 32 bit platforms.

nvoron23/tarantool,rtsisyk/tarantool,Sannis/tarantool,KlonD90/tarantool,KlonD90/tarantool,vasilenkomike/tarantool,dkorolev/tarantool,nvoron23/tarantool,KlonD90/tarantool,mejedi/tarantool,condor-the-bird/tarantool,rtsisyk/tarantool,vasilenkomike/tarantool,mejedi/tarantool,Sannis/tarantool,guard163/tarantool,Sannis/tarantool,KlonD90/tarantool,condor-the-bird/tarantool,nvoron23/tarantool,KlonD90/tarantool,dkorolev/tarantool,ocelot-inc/tarantool,mejedi/tarantool,guard163/tarantool,mejedi/tarantool,ocelot-inc/tarantool,guard163/tarantool,nvoron23/tarantool,dkorolev/tarantool,rtsisyk/tarantool,rtsisyk/tarantool,nvoron23/tarantool,guard163/tarantool,vasilenkomike/tarantool,condor-the-bird/tarantool,condor-the-bird/tarantool,guard163/tarantool,vasilenkomike/tarantool,dkorolev/tarantool,Sannis/tarantool,Sannis/tarantool,ocelot-inc/tarantool,ocelot-inc/tarantool,condor-the-bird/tarantool,dkorolev/tarantool,nvoron23/tarantool,vasilenkomike/tarantool