Commit fixes compilation of IMB driver under Cygwin.
* don't redefine PAGESIZE if defined already
* fix missing include of <asm/socket.h> - required by IO calls
Commit replaces caddr_t in IMB driver with char *. This is a wild guess
replacement, because caddr_t doesn't have to be char *. However, it shouldn't be
used and so shouldn't mmap(). So we'll have to see how things work out.
http://computer-programming-forum.com/47-c-language/556a90938d01f023.htm