undefined reference to boost::system::generic_category()

[davido]

There is BOOST_SYSTEM_NO_DEPRECATED macro that allows to ignore deprecated vars and functions. However, this not trivial for big size project (LibreOffice) that depends on dozen external libraries, that use boost, to propagate this define.

To rectify it, reverse the logic and require the folks to define BOOST_SYSTEM_DEPRECATED only when deprecated stuff is really needed, with

# ifdef BOOST_SYSTEM_DEPRECATED [...] # endif