PR 6445 (partial). Implemented system-wide utrace probes.

PR 6445 (partial).  Implemented system-wide utrace probes.
2008-08-12  David Smith  <dsmith@redhat.com>

	PR 6445 (partial)
	* tapsets.cxx (utrace_builder::build): Validates pid and allows
	probing of "*" to mean all threads.
	* stapprobes.5.in: Added note about a process path of "*" means to
	probe all threads.

2008-08-12  David Smith  <dsmith@redhat.com>

	PR 6445 (partial)
	* task_finder.c (stap_register_task_finder_target): Handles
	probing all threads.
	(__stp_utrace_attach_match_filename): Ditto.
	(stap_start_task_finder): Ditto.

2008-08-12  David Smith  <dsmith@redhat.com>

	PR 6445 (partial)
	* systemtap.base/utrace_p4.exp: Added test that probes all threads.
	* semko/utrace14.stp: New test.