perf probe: Provide perf interface for uprobes

- Enhances perf to probe user space executables and libraries.
- Enhances -F/--funcs option of "perf probe" to list possible probe points in
  an executable file or library.
- Documents userspace probing support in perf.

[ Probing a function in the executable using function name  ]
perf probe -x /bin/zsh zfree

[ Probing a library function using function name ]
perf probe -x /lib64/libc.so.6 malloc

[ list probe-able functions in an executable ]
perf probe -F -x /bin/zsh

[ list probe-able functions in an library]
perf probe -F -x /lib/libc.so.6

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Anton Arapov <anton@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux-mm <linux-mm@kvack.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20120416120909.30661.99781.sendpatchset@srdronam.in.ibm.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>