[krbdev.mit.edu #2551] Or use BYTE_ORDER :-)

[Alexandra Ellwood via RT]

Darwin also seems to define the macro BYTE_ORDER (defined to either BIG_ENDIAN or 
LITTLE_ENDIAN depending on the architecture) in endian.h.  

Heimdal checks for the presence of BYTE_ORDER and prefers it to configure-time checks.  It 
does not currently check __BIG_ENDIAN__ and __LITTLE_ENDIAN__ because they are newer 
gcc macros (although I think that is going to get fixed).