Remove duplicate static function check_permissions in slotfuncs.c and logicalfuncs.c

Hi,

We have two static check_permissions functions (one in slotfuncs.c
another in logicalfuncs.c) with the same name and same code for
checking the privileges for using replication slots. Why can't we have
a single function CheckReplicationSlotPermissions in slot.c? This way,
we can get rid of redundant code. Attaching a patch for it.

Thoughts?

Regards,
Bharath Rupireddy.