Fix up AS400 limit/offset support.  Now supports offsets with nil limits.
Fix up AS400 limit/offset support.  Now supports offsets with nil limits.

t-morgan/sequel,uhoh-itsmaciek/sequel,nju520/sequel,mpalmer/sequel,dennis-d/custom_sequel,t-morgan/sequel,uhoh-itsmaciek/sequel,offshore-safety/sequel,Marketcircle/sequel,dennis-d/custom_sequel,offshore-safety/sequel,nicohvi/sequel,offshore-safety/sequel,beni55/sequel,knut2/sequel,davidbegin/sequel,yazshel/sequel,freshpay/sequel,davidbegin/sequel,beni55/sequel,mpalmer/sequel,reubano/sequel,pfarrell/sequel,chef/sequel,yazshel/sequel,knut2/sequel,seeARMS/sequel,nju520/sequel,reubano/sequel,gferguson-gd/sequel,nicohvi/sequel,seeARMS/sequel,bigfix/sequel,pfarrell/sequel,freshpay/sequel,gferguson-gd/sequel