Use dpkg-architecture to find multiarch directory name on Debian.


git-svn-id: http://yate.null.ro/svn/yate/trunk@5852 acf43c95-373e-0410-b603-e72c3f656dc1
Use AC_TRY_LINK to check if the PostgreSQL library is linkable.


git-svn-id: http://yate.null.ro/svn/yate/trunk@5853 acf43c95-373e-0410-b603-e72c3f656dc1