[Groff] register `.pe'

[Werner LEMBERG]

It is amazing that there were still some registers which slipped
through and haven't been documented yet.

While adding documentation for \n[.w] (width of last glyph in
current environment) and \n[.n] (length of previous line in current
environment), I found the register \n[.pe].  From groff.texinfo:


 - Register: \n[.pe]
     A read-only register which is set to 1 while a page is ejected with
     the `bp' request (or by the end of input).

     Outside of traps this register is always zero.  In the following
     example, only the second call to `x' is caused by `bp'.


          .de x
          \&.pe=\\n[.pe]
          .br
          ..
          .wh 1v x
          .wh 4v x
          A line.
          .br
          Another line.
          .br
              => A line.
                        .pe=0
                        Another line.
          
                        .pe=1


   Werner