perf buildid-list: New plumbing command

With this we can list the buildids in a perf.data file so that
we can pipe them to other, distro specific tools that from the
buildids can figure out separate packages (foo-debuginfo) where
we can find the matching symtabs so that perf report can do its
job.

E.g:

[acme@doppio linux-2.6-tip]$ perf buildid-list | head -5
8e08b117e5458ad3f85da16d42d0fc5cd21c5869
520c2387a587cc5acfcf881e27dba1caaeab4b1f
ec8dd400904ddfcac8b1c343263a790f977159dc
7caedbca5a6d8ab39a7fe44bd28c07d3e14a3f3f
379bb828fd08859dbea73279f04abefabc95a6a3
[acme@doppio linux-2.6-tip]$ perf buildid-list -v | head -5
8e08b117e5458ad3f85da16d42d0fc5cd21c5869 /sbin/init
520c2387a587cc5acfcf881e27dba1caaeab4b1f /lib64/ld-2.10.1.so
ec8dd400904ddfcac8b1c343263a790f977159dc /lib64/libc-2.10.1.so
7caedbca5a6d8ab39a7fe44bd28c07d3e14a3f3f /sbin/udevd
379bb828fd08859dbea73279f04abefabc95a6a3 /lib64/libdl-2.10.1.so
[acme@doppio linux-2.6-tip]$

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <1258396365-29217-5-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>