getpagesize on mingw

[Sam Steingold]

Hi,
updating gnulib files in clisp pulled in getpagesize.m4 and getpagesize.m4,
so I decided to use them instead of the traditional clisp code.
my question is: where is the prototype for the replacement getpagesize()?
it would make sense to include unistd.h, but it is not generated on win32.
also, mingw already comes with a unistd.h (but it does not prototype 
getpagesize there) - which is why gnulib does not generate the replacement 
unistd.h.
so, I guess, I must somehow tell the build process to generate build/unistd.h 
out of the already present gllib/unistd_h.in.
so, how do I do that?
actually, maybe getpagesize.m4 should do that automatically?
thanks
Sam.