Tests: Use Perl prove as the testsuite runner

Tests: Use Perl prove as the testsuite runner

Currently the regression and unit testsuites are runned via a custom
runner script. By using the Perl prove utility, we can run the
testsuites and also gain additionnal features such as: parallel jobs,
separate testlists, etc.

This commit modify the make check target to run Perl prove as the
testsuite runner.

Testlist:

tests/unit_tests      : unit tests.
tests/fast_regression : a fast regression testsuite.
tests/long_regression : a long regression testsuite (includes slow tests such
                        as test_low_throughput and others).
tests/root_regression : a testsuite for tests that need root access
		        (mostly tests using lttng-modules and bandwith limits).

Running a testsuite:

$ cd lttng-tools/tests
$ ./run.sh <testsuite>

One can also run tests manually using prove:

$ prove --exec '' path/to/test

  OR

$ prove --exec '' - < testlist

Signed-off-by: Christian Babeux <christian.babeux@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>