[boost] [Signals] Fixed shared library issues on RC_1_33_0

From: Douglas Gregor (doug.gregor_at_[hidden])
Date: 2005-10-16 09:26:14

I've just checked in a fix for the shared library/symbol visibility  
problems with Signals. If you've had problems with this before,  
please test! It's on the RC_1_33_0 branch for the 1.33.1 beta release.

     Doug