perf tools: Fix error handling of unknown events

There was a problem with the parse_events() code not printing the
correct event name when an event was unknown and starting with an 'r'.
The source of the problem was the way raw notation was parsed.

Without the patch:
	$ perf stat -e retired_foo
	invalid event modifier: 'tired_foo'

With the patch:
	$ perf stat -e retired_foo
	invalid or unsupported event: 'retired_foo'

This also covers the case where the name of the event was not printed at
all when perf was linked with libpfm4.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20110723021043.GA20178@quad
Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>