Remove prototype for non-existent function from walreceiver.h. Tidy up by separating prototypes for functions in walreceiver.c and walreceiverfuncs.c with comments.
Remove prototype for non-existent function from walreceiver.h. Tidy up by
separating prototypes for functions in walreceiver.c and walreceiverfuncs.c
with comments.

xinzweb/gpdb,Postgres-XL/Postgres-XL,greenplum-db/gpdb,snaga/postgres-xl,ashwinstar/gpdb,arcivanov/postgres-xl,lisakowen/gpdb,postmind-net/postgres-xl,Postgres-XL/Postgres-XL,ashwinstar/gpdb,kmjungersen/PostgresXL,oberstet/postgres-xl,adam8157/gpdb,techdragon/Postgres-XL,50wu/gpdb,techdragon/Postgres-XL,snaga/postgres-xl,zeroae/postgres-xl,xinzweb/gpdb,ovr/postgres-xl,jmcatamney/gpdb,jmcatamney/gpdb,zeroae/postgres-xl,50wu/gpdb,techdragon/Postgres-XL,adam8157/gpdb,oberstet/postgres-xl,postmind-net/postgres-xl,kmjungersen/PostgresXL,lisakowen/gpdb,50wu/gpdb,jmcatamney/gpdb,Postgres-XL/Postgres-XL,xinzweb/gpdb,adam8157/gpdb,tpostgres-projects/tPostgres,yazun/postgres-xl,xinzweb/gpdb,ovr/postgres-xl,snaga/postgres-xl,ashwinstar/gpdb,Postgres-XL/Postgres-XL,oberstet/postgres-xl,50wu/gpdb,postmind-net/postgres-xl,lisakowen/gpdb,jmcatamney/gpdb,50wu/gpdb,greenplum-db/gpdb,zeroae/postgres-xl,adam8157/gpdb,arcivanov/postgres-xl,arcivanov/postgres-xl,50wu/gpdb,50wu/gpdb,ashwinstar/gpdb,50wu/gpdb,kmjungersen/PostgresXL,greenplum-db/gpdb,zeroae/postgres-xl,kmjungersen/PostgresXL,oberstet/postgres-xl,ovr/postgres-xl,lisakowen/gpdb,lisakowen/gpdb,arcivanov/postgres-xl,ashwinstar/gpdb,xinzweb/gpdb,tpostgres-projects/tPostgres,ashwinstar/gpdb,techdragon/Postgres-XL,greenplum-db/gpdb,pavanvd/postgres-xl,adam8157/gpdb,xinzweb/gpdb,adam8157/gpdb,xinzweb/gpdb,jmcatamney/gpdb,adam8157/gpdb,snaga/postgres-xl,arcivanov/postgres-xl,adam8157/gpdb,pavanvd/postgres-xl,arcivanov/postgres-xl,postmind-net/postgres-xl,tpostgres-projects/tPostgres,pavanvd/postgres-xl,lisakowen/gpdb,lisakowen/gpdb,ovr/postgres-xl,greenplum-db/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,tpostgres-projects/tPostgres,ovr/postgres-xl,pavanvd/postgres-xl,snaga/postgres-xl,yazun/postgres-xl,tpostgres-projects/tPostgres,yazun/postgres-xl,yazun/postgres-xl,ashwinstar/gpdb,kmjungersen/PostgresXL,oberstet/postgres-xl,pavanvd/postgres-xl,zeroae/postgres-xl,postmind-net/postgres-xl,techdragon/Postgres-XL,Postgres-XL/Postgres-XL,jmcatamney/gpdb,greenplum-db/gpdb,lisakowen/gpdb,yazun/postgres-xl,jmcatamney/gpdb,xinzweb/gpdb