perf trace: Add aliases for some syscalls

What we get from audit_syscall_to_name isn't what we find in the
syscalls: tracepoint events, so add the alias that allows the tool to
find prctl, fstat, fstatat and stat.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-3m9su7jhwnxvepnr3ne1du5k@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>