and related AC_SUBST() so that when back-tcl is compiled as a dynamic module we link
  -ltcl to the module and not slapd (this is the correct way to do this since the .la file
  handles giving the correct libs when we pass the module to it in the linker line with
  -dlopen). Also modified the perl backend in a similar way except that the PERL_CPPFLAGS
  always go to the module and never to slapd (slapd doesn't need them).
* build/mod.mk: added $(MODLIBS) to the dynamic module link line to accomodate module
  specific libraries. These should be defined in the back-*/Makefile.in file for each
  module (so far only back-tcl and back-perl need it).
* build/top.mk: modified the perl ldflags and cppflags slightly
* servers/slapd/Makefile.in: same here
* servers/slapd/back-perl/Makefile.in: added MODLIBS=$(MOD_PERL_LDFLAGS) for when we are
  using a dynamic module (problem, libtool wont allow linking static libs into a libtool
  lib, so unless perl's libs are compiled dynamic, then back-perl can't be a dynamic
  module. We need a test for this on perl and tcl).
* servers/slapd/back-tcl/Makefile.in: added MODLIBS=$(MOD_TCL_LIB)
* back-perl and back-tcl now compile