Add: update 'tests/benchmark' to lttng-ust v2 API

Fix: add missing files
zmalloc: attribute always_inline

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fix: Add --no-as-needed to the demo example's Makefile

Some distributions now ship with the --as-needed linker flag
set by default (Ubuntu 13.04). This will cause the linker to
remove the references to lttng-ust from the provider objects
thus causing the application to fail when preloading them.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fix: Check g++ version before compiling 'hello.cxx' test

Fixes #557