Tcl/tk 9 support

[rwmjones]

This is a first pass that at least compiles with Tcl/Tk 9.0.

The hardest part is that the old argc/argv interface for many functions has been completely removed, see https://core.tcl-lang.org/tips/doc/main/tip/647.md. My attempt to work around that is to convert the argc/argv to an object array. It ought to work, but I don't know how to test this is correct.

This requires https://github.com/garrigue/lablgl/pull/5 & https://github.com/garrigue/lablgl/pull/6

@jamesjer