- fix some typos
- document the difference between '>' and '>>'
- document the 'enable' toggle
- remove section "Defining an event-enabled tracepoint", since it's
  out-dated and sample/trace_events/ already serves this purpose.

v2: add "Updated by Li Zefan"

[ Impact: make documentation up-to-date ]
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
LKML-Reference: <4A125503.5060406@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1239479479-2603-3-git-send-email-tytso@mit.edu>
Signed-off-by: NIngo Molnar <mingo@elte.hu>