libtracevent: Build warning on 32-bit arches

[Arnaldo Carvalho de Melo]

Hi Tzvetomir,

	I noticed this:

  27 debian:experimental-x-mips    : Ok   mips-linux-gnu-gcc (Debian 8.3.0-19) 8.3.0
  29 debian:experimental-x-mipsel  : Ok   mipsel-linux-gnu-gcc (Debian 9.2.1-8) 9.2.1 20190909
  64 ubuntu:16.04-x-powerpc        : Ok   powerpc-linux-gnu-gcc (Ubuntu 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
  69 ubuntu:18.04-x-arm            : Ok   arm-linux-gnueabihf-gcc (Ubuntu/Linaro 7.5.0-3ubuntu1~18.04) 7.5.0
  71 ubuntu:18.04-x-m68k           : Ok   m68k-linux-gnu-gcc (Ubuntu 7.5.0-3ubuntu1~18.04) 7.5.0
  77 ubuntu:18.04-x-sh4            : Ok   sh4-linux-gnu-gcc (Ubuntu 7.5.0-3ubuntu1~18.04) 7.5.0

    event-parse.c: In function 'print_arg_pointer':
    event-parse.c:5262:29: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
       trace_seq_printf(s, "%p", (void *)val);
                                 ^
The cset is:

  487ae1f4a17c197a ("tools lib traceevent: Add support for more printk format specifiers")

Best regards,

- Arnaldo