arm: new way of handling ERESTART_RESTARTBLOCK

new "syscall start" flag; handled in syscall_trace() by switching
syscall number to that of syscall_restart(2).  Restarts of that
kind (ERESTART_RESTARTBLOCK) are handled by setting that bit;
syscall number is not modified until the actual call.

Change-Id: I0dac789dbb0cf26f5bf6a562f440305189676bd2
CRs-fixed: 592079
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Git-commit: 6b5c8045ecc7e726cdaa2a9d9c8e5008050e1252
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-stable.git
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>