Some SGI compilers define _SGI_COMPILER_VERSION in addition to the old
_COMPILER_VERSION preprocessor symbol. It is more distinctive, so we
should check it in case the old one is ever removed.
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.
This enhances the Fortran compiler id detection by using a source that
can compile either as free or fixed format. As long as the compiler
knows it should preprocess the source file (.F) the identification can
work. Even free-format compilers may try fixed-format parsing if the
user specifies certain flags, so we must support both.
Brad King