Implement userspace-probe regression tests

This adds regression testcases for the following userspace probe
features and should-fail scenarios.

Features:
  * ELF function location tracing works,
  * ELF C++ mangled function and method location tracing works,
  * SDT tracepoint location tracing works,
  * Implicit location type defaults to ELF location,
  * Binary found $PATH,
  * Binary found using full path,
  * Binary with colon in file name,
  * Disabling of all location types,
  * Listing of all location types,
  * Saving and loading of all location types,
  * SDT probe with one or more callsites,
  * SDT probe with arguments,
  * SDT probe in shared object,
  * SDT probe in dlopen()ed and ldpreload()ed shared object.
Should-fail:
  * Target binary does not exist,
  * Target binary not ELF file,
  * ELF symbol not found in target binary,
  * ELF symbol not a function,
  * SDT provider name not found,
  * SDT probe name not found,
  * SDT probe guarded by a semaphore.

We also make sure to disable testcases when the necessary files/tools
for them are not found:
  * Disables C++ testcases if no C++ compiler is found.
  * Disables SDT testcases if the Systemtap header files are not found.
    This is tested by trying to compile a simple C program with a SDT
    probe. If it fails, it will only disable the testcases and not the
    feature since the SDT userspace probe feature does not use this header
    for parsing.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Erica Bugden <ebugden@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>