Wrap linux specific syscall 22 (ustat)

Wrap linux specific syscall 22 (ustat)

The ustat syscall comes from pre-git linux history.  It is
deprecated in favor of statfs.  But in some cases it may
still be used.

int ustat(dev_t dev, struct ustat *ubuf); returns information
about a mounted filesystem.  dev is a device number identifying
a device containing a mounted filesystem.  ubuf is a pointer to
a ustat structure.

Declare a sys_ustat wrapper in priv_syswrap-linux.h and hook
it for {amd64,arm,arm64,mips64,nanomips,ppc32,ppc64,riscv64,\
s390x,x86}-linux using LINXY with PRE and POST handler in
syswrap-linux.c

https://bugs.kde.org/show_bug.cgi?id=506928