#11 Clean up search path mess

[Joachim Schrod]

idxstyle::*default-load-paths* is initialized with
*load-paths* before
that is set in defaults.xdy. Thus :default does not work.

We want to compute the default anyhow, to have a
relocatable xindy system. I.e., we want to set
*default-load-paths* in the xindy script. We should
provide a macro for that.

Initialization of *load-paths* in defaults.xdy does not
work either. The passed pathnames are not recognized as
directories. Eventually, the call to #'searchpath in
xindy script sets the search path!

Incidentially, the *load-paths* default is '(#P"./"
"~/lisp/**/"). I
tried to set it to something similar in interactive
mode; but CLISP
replies at require time: "wildcards are not allowed
here". But we want it, as we could do away with subdir
specification in requires. Need to check this; after
the upgrade to current CLISP.

We should do directory tree searching, too; in a
breadth first search.
This way specific modules may be specified by a path
relative to
$modules_dir. Arbitrary modules can be searched. NOTE:
The module name makeindex.xdy is a problem, then. This
might hinder our wish.

In the end, TeX users are used to kpathsea-style
behaviour. With LISP pathnames, it should be quite easy
to supply something reasonable similar.