The command tt(INCLUDELITERAL) takes one argument, a filename. The file is
included. 

The filename is not changed in any way.

Furthermore the contents of the file is included literally, not subject to
macro expansion. Character translations are allowed.

The purpose of INCLUDELITERAL is to include source code literally in the
document, as in:

verb(INCLUDELITERAL(literal.c))

This example shows how to put the contents of C file literal.c into the
document.
