linux-user: Add strace support for printing arguments of truncate()/ftruncate() and...

linux-user: Add strace support for printing arguments of truncate()/ftruncate() and getsid()

This patch implements strace argument printing functionality for following syscalls:

    * truncate, ftruncate - truncate a file to a specified length

        int truncate/truncate64(const char *path, off_t length)
        int ftruncate/ftruncate64(int fd, off_t length)
        man page: https://man7.org/linux/man-pages/man2/truncate.2.html

    * getsid - get session ID

        pid_t getsid(pid_t pid)
        man page: https://man7.org/linux/man-pages/man2/getsid.2.html

Implementation notes:

    Syscalls truncate/truncate64 take string argument types and thus a
    separate print function "print_truncate/print_truncate64" is stated in
    file "strace.list". This function is defined and implemented in "strace.c"
    by using an existing function used to print string arguments: "print_string()".
    For syscall ftruncate64, a separate printing function was also stated in
    "strace.c" as it requires a special kind of handling.
    The other syscalls have only primitive argument types, so the rest of the
    implementation was handled by stating an appropriate printing format in file
    "strace.list".
    Function "regpairs_aligned()" was cut & pasted from "syscall.c" to "qemu.h"
    as it is used by functions "print_truncate64()" and "print_ftruncate64()"
    to print the offset arguments of "truncate64()" and "ftruncate64()".

Signed-off-by: Filip Bozuta <Filip.Bozuta@syrmia.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20200811164553.27713-3-Filip.Bozuta@syrmia.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>