Expand ${...} before parsing conditions.  Closes #318

Which incidentally allows you to put conditions inside of
the variables.  Hmm... that could be useful.

The ${...} expansion is a *macro* expansion.  So it even expands
inside of '${..}' !
talloc_steal pointers, instead of just memcpy'ing them.

Hmm... we should probably update the DICT to have a "is pointer"
flag, and add a generic "pointer" to value_pair_data.  That way
this kind of code can just manipulate the underlying pointer,
without having a switch statement and multiple copies of the
similar code
More debugging