Rewrite make_h_tree.pl in shell script

Rewrite make_h_tree.pl in shell script

The current usage of make_h_tree.pl adds a build requirement of
/usr/bin/perl that we did not have prior to commit
1d6593e952ce82c778b1cd6e40c6e22ec756daf1. Do the same thing in a
bourne shell script instead, so we don't need perl.

Note that this is not as generalized as make_h_tree.pl, but it doesn't
need to be. Specifically, this does not strip a leading ../ from found
include directives (nothing in the tree that includes h/* files uses
this), and header filenames containing whitespace almost certainly do
not work correctly.

The h => sys mapping is also much more hardcoded, but that's all we
were using this for anyway.

Change-Id: If07888abfdb9e8ec822b33abed0bf744b7210a52
Reviewed-on: http://gerrit.openafs.org/6790
Reviewed-by: Russ Allbery <rra@stanford.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>