GLsizei type

Sorry for abusing this list a bit, but I think here are some of the best 
people for answering the following question (if not, please give me a hint 
where to ask instead):

What is the rationale for "GLsizei" being an "int" on all platforms I know of 
and not an "unsigned int"? Reading the description in the OpenGL spec, one 
might expect the former, but not really the latter. Is it because of some 
legacy reason with IRIS GL? Is it simply because of the name (which might be 
GLsizeui otherwise)? Or is it simply by accident? :-)

This is not an academic question, we are discussing how to standardise similar 
types for OpenAL (http://www.openal.org/), see e.g. the mail at:

   http://opensource.creative.com/pipermail/openal-devel/2005-July/000974.html

Cheers,
   S.