QLogging: Avoid infinite loop in error case

If the user code installs a message handler that uses
any API that prints logs (handled by qt_message_print)
then this will lead to an infinite loop.

This patch adds a thread local storage to check
if the message handler is done before the thread
is calling it again.

Note: This check is performed only if the compiler
supports thread_local (__declspec(thread) for MSVC).

Change-Id: I43b0460b8f39b26a18de48a5652a5e55f0b336f8
Reviewed-by: Rafael Roquetto <rafael.roquetto@kdab.com>