direct log4shib access

[wferi at niif.hu]

Hi Scott,

The memcache-store SP plugin calls log4shib::Category::debug() without
linking to the log4shib library.  This works, because the SP plugin host
provides this symbol for the plugin.  If it is the intended way, then
log4shib/log4cpp should either be declared as a public requirement in
the pkg-config file of the appropriate library, or the host CXXFLAGS/
LIBADD enumerations should be augmented with the logging libraries.  On
the other hand if these symbols aren't meant to be provided by the host,
then the plugin CXXFLAGS/LIBADD should be augmented instead. (The above
plugin is just an example illustrating the question about the intended
API usage.)
-- 
Thanks,
Feri