perf_counter tools: Use hex2u64 in more places

This has also a nice side effect, tools built on newer systems such as
fedora 10 again work on systems with older versions of glibc:

My workstation:

[acme@doppio ~]$ rpm -q glibc.x86_64
glibc-2.9-3.x86_64

Test machine:

[acme@emilia ~]$ rpm -q glibc.x86_64
glibc-2.5-24

Before:

[acme@emilia ~]$ perf
perf: /lib64/libc.so.6: version `GLIBC_2.7' not found (required by perf)
[acme@emilia ~]$ nm `which perf` | grep GLIBC_2\.7
                 U __isoc99_sscanf@@GLIBC_2.7
[acme@emilia ~]$

After:
[acme@emilia ~]$ perf
usage: perf [--version] [--help] COMMAND [ARGS]

The most commonly used perf commands are:
   record   Run a command and record its profile into perf.data
   report   Read perf.data (created by perf record) and display the
profile
   stat     Run a command and gather performance counter statistics
   top      Run a command and profile it

See 'perf help COMMAND' for more information on a specific command.
[acme@emilia ~]$ nm `which perf` | grep GLIBC_2\.7
[acme@emilia ~]$

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20090601205019.GA7805@ghostprotocols.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>