Logcat Text: fix assert when dissecting PID or TID

Per Android documentation, the PID and TID are int

Change-Id: I05326d134047315d61a873c33dd02a48d1849f8d
Reviewed-on: https://code.wireshark.org/review/3481
Reviewed-by: Evan Huus <eapache@gmail.com>
Reviewed-by: Anders Broman <a.broman58@gmail.com>