Let module depend on PostgreSQL server package.

debian/changelog

@@ -3,6 +3,7 @@ postgresql-hll (2.10.2-1) UNRELEASED; urgency=medium
   * New upstream version.
   * Move package to the PostgreSQL team.
   * Convert to pg_buildext. Closes: #876826.
+  * Let module depend on PostgreSQL server package.
   * Update copyright file.
 
  -- Christoph Berg <myon@debian.org>  Fri, 06 Apr 2018 17:00:41 +0200

debian/control

@@ -11,7 +11,7 @@ Vcs-Git: https://salsa.debian.org/postgresql/postgresql-hll.git
 
 Package: postgresql-10-hll
 Architecture: any
-Depends: ${shlibs:Depends}, ${misc:Depends}
+Depends: ${shlibs:Depends}, ${misc:Depends}, postgresql-10
 Description: HyperLogLog extension for PostgreSQL
  This PostgreSQL module introduces a new data type `hll` which is a HyperLogLog
  data structure. HyperLogLog is a fixed-size, set-like structure used for

debian/control.in

@@ -11,7 +11,7 @@ Vcs-Git: https://salsa.debian.org/postgresql/postgresql-hll.git
 
 Package: postgresql-PGVERSION-hll
 Architecture: any
-Depends: ${shlibs:Depends}, ${misc:Depends}
+Depends: ${shlibs:Depends}, ${misc:Depends}, postgresql-PGVERSION
 Description: HyperLogLog extension for PostgreSQL
  This PostgreSQL module introduces a new data type `hll` which is a HyperLogLog
  data structure. HyperLogLog is a fixed-size, set-like structure used for