perf annotate: Fix handling of goto labels that are valid hex numbers

When parsing the objdump disassembly output we can have goto labels that
are valid hex numbers and thus get confused with lines with machine
code.

Handle the common case of a label that has nothing after it and other
cases where there is just source code by validating the resulting "ip".

It is still possible that we find goto labels that are in the function
address range, but only if they are located before the real address we
should be OK.

A change in the objdump output to have a clear marker separating
addresses from the disassembly would come handy, but we would still have
to deal with older versions.

Reported-by: Gleb Natapov <gleb@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <20100722170541.GF17631@ghostprotocols.net>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>