perf ui browser: Don't use windows, slang is enough

They are useless and take away precious columns and lines, so stop using
windows.

One more step in removing newt code, that after all is not being useful
at all for the coalescing TUI model in perf.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Cc: Christoph Hellwig <hch@infradead.org>
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: <20100822082003.GB7365@infradead.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>