tracing/infrastructure: separate event tracer from event support

Add a new config option, CONFIG_EVENT_TRACING that gets selected
when CONFIG_TRACING is selected and adds everything needed by the stuff
in trace_export - basically all the event tracing support needed by e.g.
bprint, minus the actual events, which are only included if
CONFIG_EVENT_TRACER is selected.

So CONFIG_EVENT_TRACER can be used to turn on or off the generated events
(what I think of as the 'event tracer'), while CONFIG_EVENT_TRACING turns
on or off the base event tracing support used by both the event tracer and
the other things such as bprint that can't be configured out.

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: fweisbec@gmail.com
LKML-Reference: <1239178441.10295.34.camel@tropicana>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/Kconfig

@@ -48,6 +48,9 @@ config FTRACE_NMI_ENTER
        depends on HAVE_FTRACE_NMI_ENTER
        default y
 
+config EVENT_TRACING
+	bool
+
 config TRACING
 	bool
 	select DEBUG_FS
@@ -56,6 +59,7 @@ config TRACING
 	select TRACEPOINTS
 	select NOP_TRACER
 	select BINARY_PRINTF
+	select EVENT_TRACING
 
 #
 # Minimum requirements an architecture has to meet for us to