Made tests build in multithreaded environment by default (this can still be changed by specifying threading=single in the command line). The util_once_block test updated to be usable in singlethreaded builds.

svn path=/trunk/libs/log/; revision=83977
Removed deprecated macros usage.

svn path=/trunk/boost/log/; revision=83978
Added workarounds to eliminate broken links in the generated docs.

svn path=/trunk/boost/log/; revision=83979