Another bit of ISO C conversion...

["Zack Weinberg" <zack at codesourcery dot com>]

We've had a lot of people put in time to convert GCC to ISO C style,
and I want to say that I appreciate all of that effort.  There's one
transformation that hasn't been getting done, though: use of #elif.
K&R C didn't have this directive so we have lots of nested #if
blocks.  For example, from hwint.h:

#if HOST_BITS_PER_LONG >= 64 || !defined NEED_64BIT_HOST_WIDE_INT
#   define HOST_BITS_PER_WIDE_INT HOST_BITS_PER_LONG
#   define HOST_WIDE_INT long
#else
# if HOST_BITS_PER_LONGLONG >= 64
#   define HOST_BITS_PER_WIDE_INT HOST_BITS_PER_LONGLONG
#   define HOST_WIDE_INT long long
# else
#  if HOST_BITS_PER___INT64 >= 64
#   define HOST_BITS_PER_WIDE_INT HOST_BITS_PER___INT64
#   define HOST_WIDE_INT __int64
#  else
    #error "Unable to find a suitable type for HOST_WIDE_INT"
#  endif
# endif
#endif

This can become

#if HOST_BITS_PER_LONG >= 64 || !defined NEED_64BIT_HOST_WIDE_INT
#   define HOST_BITS_PER_WIDE_INT HOST_BITS_PER_LONG
#   define HOST_WIDE_INT long
#elif HOST_BITS_PER_LONGLONG >= 64
#   define HOST_BITS_PER_WIDE_INT HOST_BITS_PER_LONGLONG
#   define HOST_WIDE_INT long long
#elif HOST_BITS_PER___INT64 >= 64
#   define HOST_BITS_PER_WIDE_INT HOST_BITS_PER___INT64
#   define HOST_WIDE_INT __int64
#else
#   error "Unable to find a suitable type for HOST_WIDE_INT"
#endif

which is simpler, easier to read, and easier to modify.  

Note also that it is no longer necessary to indent the leading # of 
an #error directive; or, turnabout, it is no longer necessary to write
the leading # of any directive in column 1, so this becomes a style
decision.

zw