Add custom delimiter support for update_paths, hack in special case for TCLLIBPATH

[Micket]

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TCLLIBPATH (and nothing else as far as I know) requires spaces instead of : as the path delimiter.

Currently, the easyconfigs that set TCLLIBPATH are broken (if you load more than one) See https://github.com/easybuilders/easybuild-easyconfigs/pull/20197#issuecomment-2016750812 https://github.com/search?q=repo%3Aeasybuilders%2Feasybuild-easyconfigs%20TCLLIBPATH&type=code BTL, Graphviz, bwidget.

I opted to just hack in the special case for TCLLIBPATH, but i suppose it could be brought up even further, somehow making this an option for the easyconfigs? I don't really see how one would do this though, where we would add such a field?

modextrapaths_spaces = {
    'TCLLIBPATH': 'lib/tcl8.6',
}

meh...

Disclaimer: completely untested.

Edit: and of course i should be adding a test, haven't had time.