perf annotate: Move locking to struct annotation

Since we'll need it when implementing the live annotate TUI browser.

This also simplifies things a bit by having the list head for the source
code to be in the dynamicly allocated part of struct annotation, that
way we don't have to pass it around, it can be found from the struct
symbol that is passed everywhere.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>