Fix for #537 for older SQLite versions.
Fix for #537 for older SQLite versions.

new-xiaji/peewee,wenxer/peewee,new-xiaji/peewee,coleifer/peewee,coreos/peewee,coreos/peewee,fuzeman/peewee,bopo/peewee,jnovinger/peewee,py4a/peewee,mackjoner/peewee,jarrahwu/peewee,ronyb29/peewee,coreos/peewee,Dipsomaniac/peewee,lez/peewee,zhang625272514/peewee,coleifer/peewee,Dipsomaniac/peewee,softside/peewee,Sunzhifeng/peewee,fuzeman/peewee,zhang625272514/peewee,teserak/peewee,zhang625272514/peewee,coleifer/peewee,ghukill/peewee,Sunzhifeng/peewee,stas/peewee,new-xiaji/peewee,Sunzhifeng/peewee,wenxer/peewee,jarrahwu/peewee,bopo/peewee,jnovinger/peewee,Dipsomaniac/peewee,bopo/peewee,jarrahwu/peewee