Ensure that unistd.h is included on Linux
Ensure that unistd.h is included on Linux

(or anywhere except non-Cygwin Windows, to be precise)

Bug reported by László Böszörményi

libexpat/libexpat,libexpat/libexpat,libexpat/libexpat,libexpat/libexpat,libexpat/libexpat,libexpat/libexpat