The SWAP16() macro is broken.

  unsigned u = SWAP16(0x1234);

u will be 0x123412 instead of 0x3412.

Here's a fix.

I believe that the SWAP32() macro will also break in a similar
way on systems where "int" is larger than 32 bits, but I have
no way to test that conjecture.

-- 
Grant Edwards
grante@visi.com