perf tools: Moving code in header.c

Needed for later changes. No modified functionality.

Cc: Ingo Molnar <mingo@elte.hu>
Link: http://lkml.kernel.org/r/1328884916-5901-1-git-send-email-robert.richter@amd.com


Signed-off-by: Robert Richter <robert.richter@amd.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>