tools lib traceevent: Simplify pointer print logic and fix %pF

When processing %pX in pretty_print(), simplify the logic slightly by
incrementing the ptr to the format string if isalnum(ptr[1]) is true.
This follows the logic a bit more closely to what is in the kernel.

Also, this fixes a small bug where %pF was not giving the offset of the
function.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20180112004822.260262257@goodmis.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>