Use sysconf(_SC_PAGESIZE) instead of hardcoded PAGE_SHIFT

PAGE_SHIFT couldn't be reliably obtained at compile time,
thanks to Chris Metcalf for the hint.

* mem.c: Do not include <sys/user.h>.
[SH64] Do not include <asm/page.h>.
(get_pagesize): New function.
(sys_mmap_pgoff, sys_old_mmap_pgoff): Use it.
1 file changed