doc pretty-print new options

[Kevin Ryde]

More recent stuff not yet in the manual,

        * misc-modules.texi (Pretty Printing): Add new keyword options, break
        example to avoid long line.

New text:

     The further KEYWORD-OPTIONS are keywords and parameters as follows,

    #:display? FLAG
          If FLAG is true then print using `display'.  The default is
          `#f' which means use `write' style.  (*note Writing::)

    #:per-line-prefix STRING
          Print the given STRING as a prefix on each line.  The default
          is no prefix.

    #:width COLUMNS
          Print within the given COLUMNS.  The default is 79.

NEWS.pretty.diff
Description: Text document

misc-modules.texi.pretty.diff
Description: Text document