Add a "silent" variant of \incipit

In my collection, I have one poem where I don't have a title, but I don't want the ToP to show the incipit in quite the same form as in the actual poem. (As it happens, the first line puts some words in quotation marks, and I want to leave those marks out in the ToP.) Thus I wanted a new command. I had thought to make it be ``\incipit*``, a starred form, but that proved too much of a challenge for my intermediate LaTeX knowledge.

This is my first experience with the literate-programming system; I tried to make my additions fit the surrounding code, but this, and the documentation, could undoubtedly be improved.