Fixed inheritance from std::exception (const correctness of what()). This required declaring m_what mutable.
Created a multithreaded unit test.
Created an automatic exception thrower for unhandled errors.
Ported from previous proof of concept the threading primitves and made them production level (with error checking).
Added unit tests for threading primitives.

Removed the unit tests from the imake packaging as it the tests do not compile in imake, which will be gone soon.

Lowercased/Upercased some namespace/class names for homogeneity.

Fixed (and simplified) backtrace that went wrong when demangling a function name longer than 200 characters.

when dealing with double copy recalls.

Proper fix by defining a new RECALLJOB_SELECTED2NDCOPY state instead
of hijacking the (deprecated) fileTransactionId.

Removed the now duplicated backtrace and adapted the code where needed.

assignment operator of th Exception class.  Not only your friends
(classes) can play with your private parts (m_message and m_serrno) but
so can you.

    castor::exception::AlreadyInitialized

cancelled

resilient to hardware unavailability.

broken when dealing with double copy recalls.

This fix is not optimal: we're still using fileTransactionId being NULL
as a flag while we should really create an extra status
RECALLJOB_SELECTED2ND or SELECTEDSHADOW. Not on this hot fix...

This commit also includes a simpler way to select new recall candidates,
which makes it more immune to bugs like the above.
Plus a fix related to the precision used to check if a file was
overwritten while being recalled.

Added an std::exception::Backtrace class, providing a backtrace attached to all exception.
Fixed minor side effects (virtual destructors, catch orders) induced by the inheritance from std::exception.