tools lib traceevent: Rename struct cmdline to struct tep_cmdline

In order to make libtraceevent a proper library, variables, data
structures and functions should have a unique prefix to prevent name
space conflicts. That prefix will be "tep_".

This patch renames 'struct cmdline' to 'struct tep_cmdline'.

Signed-off-by: Tzvetomir Stoyanov <tstoyanov@vmware.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20181201040852.358871851@goodmis.org


Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>