add a test suite for tar module
fix for bug 6b7aa0aecca6fdce12589884c3c9ea2b50c92ad4, tar::skip silently 
truncates at 65536
fix setup1 script for tar.test so that tests don't pollute each other
Fixed the testsuite up somewhat.
(1) Moved helper code into separate file.
(2) Replaced helper code blocks in variables with proper procedures.
(3) Simplified setup1, cleanup1
    No need to search for and create lots of temp dirs in setup,
    just remove the directory in cleanup. Now use single temp dir,
    fixed name.
(4) Fixed setup of tests in general
(4a) Added emacs mode marker to get proper Tcl mode.
(4b) Added missing Tcl 8.5 requirement
(4c) Use canonical 'use' command for access to local package (memchan).
(5) Constrained the one test requiring Tcl 8.6 (zlib)

It is not yet clear to me why the 'stream' helper (to create a large
file) is so complex.
The issue with the skip code was not the limit to 64K, but how the
code
(a) assumed the wrong type for the result of 'read' (number of bytes,
    but is the read data), and
(b) mis-handled short reads.

Using 'string length' to convert the result type into what was needed,
and using the proper condition was what fixed the issue, and not
getting rid of the limit.

I have now re-instated the limit, with in-code explanation of why it
makes sense, and verified that this still passes the testsuite.

I further changed the variable names to be much more self-documenting
as well.
Bumped package version, updated logs, ready to merge.
Fixed ticket [6b7aa0aecc].
Update to head of trunk.
Get tar fixes back.