The SGI preprocessor /usr/lib/cpp produces bad output on this code:

  #if 1
  A
  #elif 1
  B
  #else
  C
  #endif

Both 'A' and 'C' appear in the output!  We work around the problem by
using '#elif 1' instead of '#else'.

This fixes detection of the SGI Fortran compiler id in -o32 mode.