examples.wrappers: Scripts to use with option --wrapper.

Scripts to use with command line option --wrapper.

* dummy.sh    Do nothing (use as a template).
* strace.sh   Run process on strace, output: strace.log.<pid>
* ltrace.sh   Run process on  ltrace, output: ltrace.log.<pid>
* perf.sh     Record process on perf, output: perf.data.<pid>
* valgrind.sh Run process on valgrind's memcheck, output: valgrind.log.<pid>

Usage:

  avocado run datadir --wrapper examples/wrappers/strace.sh
  avocado run datadir \
              --wrapper examples/wrappers/ltrace.sh:make \
              --wrapper examples/wrappers/perf.sh:datadir \

Signed-off-by: Rudá Moura <rmoura@redhat.com>

Valgrind.

Signed-off-by: Rudá Moura <rmoura@redhat.com>
selftests: Add functional tests for --wrapper feature.

Add some functional tests to explore the --wrapper feature.

Signed-off-by: Rudá Moura <rmoura@redhat.com>
docs+man: Add documentation for the --wrapper feature.

Add documentation manual page part for the command line
feature `--wrapper`.

Signed-off-by: Rudá Moura <rmoura@redhat.com>