Initial checkin of some changes related to making PS/PDF output

Initial checkin of some changes related to making PS/PDF output
from "man -l -Tps" look better. The current changes:

  - render synopsis and verbatim sections in a monospace/code font

  - put a light-grey background behind all programlisting, screen,
    and literallayout instances

  - prevent SH heads in PS output from being rendered in uppercase
    (as they are in console output)

  - also display xrefs to SH heads in PS output in normal case
    (instead of uppercase)

  - draw a line under SH heads in PS output

The changes made to the code to support the above features were:

  - added some embedded/custom macros: one for conditionally
    upper-casing SH x-refs, one for redefining the SH macro
    itself, with some conditional handling for PS output, and
    finally a macro for putting a background/screen (filled box)
    around a block of text (e.g., a program listing) in PS output

  - added utility templates for wrapping blocks of text in code
    font; also templates for inline code font