Currently wapp cannot be loaded in a slave interp or separate thread because there ::argv0 is not set.

<verbatim>
interp create wapp

wapp eval {
  source ./wapp.tcl
  wapp-start {}
}
</verbatim>

Fails with:

<verbatim>
can't read "argv0": no such variable
    while executing
"file normalize $argv0"
    (procedure "wappInt-http-readable-unsafe" line 20)
    invoked from within
"wappInt-http-readable-unsafe sock7fd4a78a0290"
    invoked from within
"catch [list wappInt-http-readable-unsafe $chan] msg"
</verbatim>