doc: Shorten some long subsection names in Manual. Remove excess spaces from ends of @menu definitions. * doc/interpreter/arith.txi, doc/interpreter/basics.txi, doc/interpreter/bugs.txi, doc/interpreter/container.txi, doc/interpreter/data.txi, doc/interpreter/diagperm.txi, doc/interpreter/diffeq.txi, doc/interpreter/emacs.txi, doc/interpreter/expr.txi, doc/interpreter/external.txi, doc/interpreter/func.txi, doc/interpreter/grammar.txi, doc/interpreter/gui.txi, doc/interpreter/install.txi, doc/interpreter/intro.txi, doc/interpreter/io.txi, doc/interpreter/java.txi, doc/interpreter/linalg.txi, doc/interpreter/matrix.txi, doc/interpreter/nonlin.txi, doc/interpreter/numbers.txi, doc/interpreter/octave.texi, doc/interpreter/optim.txi, doc/interpreter/plot.txi, doc/interpreter/preface.txi, doc/interpreter/quad.txi, doc/interpreter/sparse.txi, doc/interpreter/stats.txi, doc/interpreter/stmt.txi, doc/interpreter/strings.txi, doc/interpreter/system.txi, doc/interpreter/var.txi: Shorten some long subsection names in Manual. Remove excess spaces from ends of @menu definitions.

      subroutine fortsub (n, a, s)
      implicit none
      character*(*) s
      real*8 a(*)
      integer*4 i, n, ioerr
      do i = 1, n
        if (a(i) .eq. 0d0) then
          call xstopx ('fortsub: divide by zero')
        else
          a(i) = 1d0 / a(i)
        endif
      enddo
      write (unit = s, fmt = '(a,i3,a,a)', iostat = ioerr)
     $       'There are ', n,
     $       ' values in the input vector', char(0)
      if (ioerr .ne. 0) then
        call xstopx ('fortsub: error writing string')
      endif
      return
      end