Don't override existing :ruby_default schema entry in Database#schema
Don't override existing :ruby_default schema entry in Database#schema

This change will allow adapters to set it inside schema_parse_table,
which is necessary if the ruby default depends on information other
than the :default and :type entries.

davidbegin/sequel,knut2/sequel,yazshel/sequel,mpalmer/sequel,mpalmer/sequel,seeARMS/sequel,knut2/sequel,pfarrell/sequel,nju520/sequel,reubano/sequel,pfarrell/sequel,nju520/sequel,gferguson-gd/sequel,seeARMS/sequel,t-morgan/sequel,beni55/sequel,t-morgan/sequel,yazshel/sequel,davidbegin/sequel,gferguson-gd/sequel,nicohvi/sequel,beni55/sequel,uhoh-itsmaciek/sequel,uhoh-itsmaciek/sequel,reubano/sequel,nicohvi/sequel