[doxygen] Possible bug in doxygen 1.8.5

Hi,

There was a problem building the interprocess documentation on doxygen
1.8.5, so I've downgraded to doxygen 1.8.3.1 which works okay. The
issue was with the use of '@cond' in
'boost/interprocess/allocators/adaptive_pool.hpp'. For some reason
doxygen was including some of the adaptive_pool_base methods as free
functions, including the destructor '~adaptive_pool_base'. I probably
won't find the time to investigate this issue, so I'll be sticking
with the old version for now. But if anyone fancies investigating
(e.g. checking if there's already a bug report in Doxygen's bugzilla,
creating a small test case, checking if it also happens in a normal
doxygen run or just in the xml output) that would be very helpful.

thanks,

Daniel