perf probe: Remove xstrdup()/xstrndup() from util/probe-{event, finder}.c

Remove all xstr*dup() calls from util/probe-{event,finder}.c since
it may cause 'sudden death' in utility functions and it makes
reusing it from other code difficult.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20100412171756.3790.89607.stgit@localhost6.localdomain6>
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>