[Groff] new .linetabs request

[Werner LEMBERG]

If finally implemented `line-tabs' mode -- this is an extension
(i.e. off by default), avoiding compatibility problems.

Enjoy!


    Werner


>From the NEWS file:

  The new request `linetabs' controls the `line-tabs' mode.  In
  line-tabs mode, tab distances are computed relative to the (current)
  output line.  Otherwise they are taken relative to the input line.
  For example, the following


    .ds x a\t\c
    .ds y b\t\c
    .ds z c
    .ta 1i 3i
    \*x
    \*y
    \*z

  yields

    a         b         c

  In line-tabs mode, the same code gives

    a         b                   c