CPP macro for Byte-order

[Richard Earnshaw]

> 
> On the other hand, the gcc backends define BITS_BIG_ENDIAN,
> BYTES_BIG_ENDIAN, and WORDS_BIG_ENDIAN (you would want BYTES_BIG_ENDIAN to
> solve the problem of detecting NaNs and the like). 

It is a common mistake to confuse the INTEGER endian settings with the 
requirements for floating point numbers.  The two need not be related, and 
on many architectures aren't.

Please keep these separate.

R.