Fix rewrite flag (retain previous information in modify_binary_op) and remove thinking error in conflict detection (that prohibited a number of rewrites).
Fix rewrite flag (retain previous information in modify_binary_op)
and remove thinking error in conflict detection (that prohibited
a number of rewrites).

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb