Reduce console clutter

With this changeset, for each sys_vgui call at most one line of the Tcl code is printed, starting at the first non-whitespace character. I think that this is a reasonable compromise which keeps the messages informative and useful for debugging purposes, while also cutting back the console clutter to a sane level which can be tolerated by end users.

Rationale: Right now the sheer amount of Old command messages due to some externals (most notably flext-based ones) overwhelms not only the user, but also the program itself, so that patches containing these externals (such as the fluid~-help patch) can't even be opened in purr-data. The proposed changeset considerably reduces the clutter, so that these patches work again (minus the editing features that are supposed to be implemented by the Tcl code, of course; but at least those patches can be opened and all essential functionality will be there).