perf tools: Fix make tarballs

perf tools: Fix make tarballs

The patch series that introduced the top level tools/ makefile and the
libtraceevent broke this feature where files needed to build in a
detached tarball were not included in the MANIFEST file and thus not
included in the tarball.

Fix it by adding the relevant files to the MANIFEST.

Cc: Borislav Petkov <borislav.petkov@amd.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/n/tip-z3mjj74927xvqwhlmu18kj80@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>