Create an empty ewoc.
The ewoc will be inserted in the current buffer at the current position.
PRETTY-PRINTER should be a function that takes one argument, an
element, and inserts a string representing it in the buffer (at
point). The string PRETTY-PRINTER inserts may be empty or span
several lines. The PRETTY-PRINTER should use `insert', and not
Optional second and third arguments HEADER and FOOTER are strings,
possibly empty, that will always be present at the top and bottom,
respectively, of the ewoc.
Normally, a newline is automatically inserted after the header,
the footer and every node's printed representation. Optional
fourth arg NOSEP non-nil inhibits this. (fn PRETTY-PRINTER &optional HEADER FOOTER NOSEP)