tools lib traceevent: Rename internal parser related APIs

tools lib traceevent: Rename internal parser related APIs

In order to make libtraceevent into a proper library, variables, data
structures and functions require a unique prefix to prevent name space
conflicts. That prefix will be "tep_" and not "pevent_". This changes
APIs: pevent_buffer_init, pevent_read_token, pevent_free_token,
pevent_peek_char, pevent_get_input_buf, pevent_get_input_buf_ptr

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
Cc: linux-trace-devel@vger.kernel.org
Link: http://lkml.kernel.org/r/20180808180703.275281085@goodmis.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>