Give 'a_expr ::= a_expr Op' production a slightly lower precedence than Op, so that the sequence 'a_expr Op Op a_expr' will be parsed as a_expr Op (Op a_expr) not (a_expr Op) Op a_expr as formerly.  In other words, prefer treating user-defined operators as prefix operators to treating them as postfix operators, when there is an ambiguity. Also clean up a couple of other infelicities in production priority assignment --- for example, BETWEEN wasn't being given the intended priority, but that of AND.
Give 'a_expr ::= a_expr Op' production a slightly lower precedence than
Op, so that the sequence 'a_expr Op Op a_expr' will be parsed as
a_expr Op (Op a_expr) not (a_expr Op) Op a_expr as formerly.  In other
words, prefer treating user-defined operators as prefix operators to
treating them as postfix operators, when there is an ambiguity.
Also clean up a couple of other infelicities in production priority
assignment --- for example, BETWEEN wasn't being given the intended
priority, but that of AND.

zeroae/postgres-xl,cjcjameson/gpdb,kaknikhil/gpdb,janebeckman/gpdb,adam8157/gpdb,chrishajas/gpdb,Chibin/gpdb,Quikling/gpdb,foyzur/gpdb,lpetrov-pivotal/gpdb,yuanzhao/gpdb,CraigHarris/gpdb,Postgres-XL/Postgres-XL,tangp3/gpdb,snaga/postgres-xl,yuanzhao/gpdb,xuegang/gpdb,lintzc/gpdb,greenplum-db/gpdb,kaknikhil/gpdb,royc1/gpdb,snaga/postgres-xl,edespino/gpdb,snaga/postgres-xl,Postgres-XL/Postgres-XL,xinzweb/gpdb,greenplum-db/gpdb,Quikling/gpdb,royc1/gpdb,zaksoup/gpdb,50wu/gpdb,zaksoup/gpdb,rubikloud/gpdb,Postgres-XL/Postgres-XL,CraigHarris/gpdb,janebeckman/gpdb,lisakowen/gpdb,yuanzhao/gpdb,janebeckman/gpdb,greenplum-db/gpdb,xuegang/gpdb,oberstet/postgres-xl,randomtask1155/gpdb,lpetrov-pivotal/gpdb,cjcjameson/gpdb,royc1/gpdb,lisakowen/gpdb,50wu/gpdb,randomtask1155/gpdb,pavanvd/postgres-xl,janebeckman/gpdb,zeroae/postgres-xl,50wu/gpdb,arcivanov/postgres-xl,royc1/gpdb,Quikling/gpdb,ahachete/gpdb,chrishajas/gpdb,lisakowen/gpdb,kmjungersen/PostgresXL,xuegang/gpdb,atris/gpdb,0x0FFF/gpdb,ashwinstar/gpdb,atris/gpdb,janebeckman/gpdb,arcivanov/postgres-xl,tangp3/gpdb,rvs/gpdb,0x0FFF/gpdb,lintzc/gpdb,kaknikhil/gpdb,yuanzhao/gpdb,ashwinstar/gpdb,Quikling/gpdb,kaknikhil/gpdb,adam8157/gpdb,adam8157/gpdb,ahachete/gpdb,cjcjameson/gpdb,50wu/gpdb,lisakowen/gpdb,edespino/gpdb,ovr/postgres-xl,CraigHarris/gpdb,Chibin/gpdb,foyzur/gpdb,janebeckman/gpdb,CraigHarris/gpdb,jmcatamney/gpdb,lisakowen/gpdb,jmcatamney/gpdb,pavanvd/postgres-xl,kaknikhil/gpdb,chrishajas/gpdb,lintzc/gpdb,lintzc/gpdb,zaksoup/gpdb,greenplum-db/gpdb,atris/gpdb,adam8157/gpdb,pavanvd/postgres-xl,pavanvd/postgres-xl,ashwinstar/gpdb,oberstet/postgres-xl,cjcjameson/gpdb,randomtask1155/gpdb,snaga/postgres-xl,xinzweb/gpdb,edespino/gpdb,rubikloud/gpdb,50wu/gpdb,ashwinstar/gpdb,Chibin/gpdb,foyzur/gpdb,0x0FFF/gpdb,50wu/gpdb,jmcatamney/gpdb,foyzur/gpdb,ahachete/gpdb,zeroae/postgres-xl,chrishajas/gpdb,postmind-net/postgres-xl,kmjungersen/PostgresXL,lisakowen/gpdb,atris/gpdb,oberstet/postgres-xl,edespino/gpdb,cjcjameson/gpdb,jmcatamney/gpdb,CraigHarris/gpdb,yuanzhao/gpdb,edespino/gpdb,50wu/gpdb,royc1/gpdb,foyzur/gpdb,jmcatamney/gpdb,randomtask1155/gpdb,tpostgres-projects/tPostgres,0x0FFF/gpdb,cjcjameson/gpdb,xuegang/gpdb,edespino/gpdb,CraigHarris/gpdb,rubikloud/gpdb,Chibin/gpdb,Chibin/gpdb,tpostgres-projects/tPostgres,yazun/postgres-xl,tpostgres-projects/tPostgres,ahachete/gpdb,lpetrov-pivotal/gpdb,Chibin/gpdb,postmind-net/postgres-xl,Chibin/gpdb,0x0FFF/gpdb,tangp3/gpdb,kmjungersen/PostgresXL,ovr/postgres-xl,zaksoup/gpdb,zeroae/postgres-xl,royc1/gpdb,jmcatamney/gpdb,Postgres-XL/Postgres-XL,ashwinstar/gpdb,xuegang/gpdb,lpetrov-pivotal/gpdb,rvs/gpdb,0x0FFF/gpdb,arcivanov/postgres-xl,greenplum-db/gpdb,kaknikhil/gpdb,atris/gpdb,lintzc/gpdb,lisakowen/gpdb,pavanvd/postgres-xl,jmcatamney/gpdb,cjcjameson/gpdb,foyzur/gpdb,Quikling/gpdb,yuanzhao/gpdb,edespino/gpdb,tangp3/gpdb,Chibin/gpdb,Quikling/gpdb,0x0FFF/gpdb,edespino/gpdb,ahachete/gpdb,techdragon/Postgres-XL,lpetrov-pivotal/gpdb,yazun/postgres-xl,arcivanov/postgres-xl,xuegang/gpdb,kmjungersen/PostgresXL,randomtask1155/gpdb,yazun/postgres-xl,ahachete/gpdb,xuegang/gpdb,lintzc/gpdb,Postgres-XL/Postgres-XL,rvs/gpdb,atris/gpdb,lpetrov-pivotal/gpdb,techdragon/Postgres-XL,Chibin/gpdb,postmind-net/postgres-xl,edespino/gpdb,xinzweb/gpdb,adam8157/gpdb,rubikloud/gpdb,techdragon/Postgres-XL,lintzc/gpdb,kaknikhil/gpdb,chrishajas/gpdb,tpostgres-projects/tPostgres,Chibin/gpdb,rubikloud/gpdb,arcivanov/postgres-xl,chrishajas/gpdb,greenplum-db/gpdb,techdragon/Postgres-XL,randomtask1155/gpdb,zaksoup/gpdb,janebeckman/gpdb,janebeckman/gpdb,Quikling/gpdb,adam8157/gpdb,yazun/postgres-xl,tangp3/gpdb,CraigHarris/gpdb,zeroae/postgres-xl,xuegang/gpdb,ahachete/gpdb,tangp3/gpdb,kaknikhil/gpdb,greenplum-db/gpdb,edespino/gpdb,rvs/gpdb,rubikloud/gpdb,CraigHarris/gpdb,Quikling/gpdb,yuanzhao/gpdb,randomtask1155/gpdb,rubikloud/gpdb,chrishajas/gpdb,0x0FFF/gpdb,zaksoup/gpdb,rvs/gpdb,yuanzhao/gpdb,foyzur/gpdb,lintzc/gpdb,Quikling/gpdb,jmcatamney/gpdb,ovr/postgres-xl,xinzweb/gpdb,tpostgres-projects/tPostgres,randomtask1155/gpdb,Quikling/gpdb,rubikloud/gpdb,cjcjameson/gpdb,ovr/postgres-xl,atris/gpdb,lpetrov-pivotal/gpdb,rvs/gpdb,lpetrov-pivotal/gpdb,kaknikhil/gpdb,ahachete/gpdb,ovr/postgres-xl,cjcjameson/gpdb,arcivanov/postgres-xl,ashwinstar/gpdb,xinzweb/gpdb,yuanzhao/gpdb,rvs/gpdb,yazun/postgres-xl,lisakowen/gpdb,rvs/gpdb,royc1/gpdb,tangp3/gpdb,oberstet/postgres-xl,techdragon/Postgres-XL,adam8157/gpdb,rvs/gpdb,kaknikhil/gpdb,foyzur/gpdb,atris/gpdb,royc1/gpdb,postmind-net/postgres-xl,zaksoup/gpdb,yuanzhao/gpdb,rvs/gpdb,50wu/gpdb,lintzc/gpdb,chrishajas/gpdb,CraigHarris/gpdb,oberstet/postgres-xl,xinzweb/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,xinzweb/gpdb,cjcjameson/gpdb,xinzweb/gpdb,janebeckman/gpdb,tangp3/gpdb,xuegang/gpdb,janebeckman/gpdb,zaksoup/gpdb,kmjungersen/PostgresXL,snaga/postgres-xl,postmind-net/postgres-xl,adam8157/gpdb,ashwinstar/gpdb