gcc vs Darwin memcmp

[Dale Johannesen]

Darwin's memcmp has semantics that are an extension of the language 
standard:

      The memcmp() function returns zero if the two strings are 
identical, oth-
      erwise returns the difference between the first two differing bytes
      (treated as unsigned char values, so that `\200' is greater than 
`\0',
      for example).

gcc's x86 inline expansion of memcmp doesn't do this, so I need to fix 
it.  Is there
interest in having this in mainline, and if so how would you like it 
controlled?