Fixed error installation on non standard postgres db port

Installation script was missing from `PGPORT` environment setup. That's
why it's can't install bareos on systems with non standard postgres
port. User gets error about connection problem and can't install. That's
PR will fix that error.

core/platforms/win32/winbareos.nsi

@@ -270,7 +270,8 @@ ${EndIf}
       LogEx::Write "PostgresPath=$PostgresPath"
 
 
-    # set postgres username and password in environment
+    # set postgres port, username and password in environment
+    System::Call 'kernel32::SetEnvironmentVariable(t "PGPORT", t "$DbPort")i.r0'
     System::Call 'kernel32::SetEnvironmentVariable(t "PGUSER", t "$DbAdminUser")i.r0'
     System::Call 'kernel32::SetEnvironmentVariable(t "PGPASSWORD", t "$DbAdminPassword")i.r0'