main/pllua: rename to postgresql-pllua

It's an extension for PostgreSQL, so it should be prefixed with
postgresql-, the same as other extensions in aports.

main/pllua/APKBUILD → main/postgresql-pllua/APKBUILD

 # Contributor: Michael Mason <ms13sp@gmail.com>
 # Contributor: Jakub Jirutka <jakub@jirutka.cz>
 # Maintainer: Michael Mason <ms13sp@gmail.com>
-pkgname=pllua
+pkgname=postgresql-pllua
 _pkgname=pllua-ng
 pkgver=2.0
 _pkgver="REL_${pkgver//./_}"
@@ -18,6 +18,8 @@ case "$CARCH" in
 esac
 makedepends="postgresql-dev $_lua-dev"
 options="!check"  # tests require running PostgreSQL
+provides="pllua=$pkgver-r$pkgrel"  # for backward compatibility
+replaces="pllua"  # for backward compatibility
 subpackages="$pkgname-dev"
 source="https://github.com/RhodiumToad/$_pkgname/archive/$_pkgver/$_pkgname-$_pkgver.tar.gz"
 builddir="$srcdir/$_pkgname-$_pkgver"