[boost] [regex] Drawing attention to link issue

Hello, The build flags for shared libraries are changing right now in b2. See https://github.com/boostorg/boost/pull/190 for more info. The thing is that Boost.Regex fails to link with those new flags, probably because of the https://github.com/boostorg/regex/issues/49 issue. If there's no simple solution for the above case, then please merge the https://github.com/boostorg/regex/pull/66/ . It should help. Thanks in advance!