perf list: Fix max event string size

perf list: Fix max event string size

Recent stalled-cycles event names were larger than the 40 chars printout
used by perf list.

Extend that, make it robust for future extensions and also adjust alignments
in face of wider event names.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/n/tip-7y40wib8n009io7hjpn1dsrm@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>