Update tar.tcl for progress bar callback

[Meshparts]

Update of tar.tcl to support optional progress bar callback. The new optional parameter can be added to the args list of tar::create like below:

tar::create $fd $paths -chan -progress [list ::ProgressBar]

The procedure ::UIProgressBar should be defined as in the case of http package, only that a token is not needed here:

proc Progress {total current} {
## Update a global variable that is linked to the progress bar widget
}

Hello. Attention please

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This is not the location where Tcllib development takes place.

We are not tracking issues entered here. With the exception of the
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Please go to the
official location of the sources
and enter your ticket into the
official ticket tracker
instead.

Thank you for your consideration.