[boost] [config] Major upgrade to Boost.Config symbol visibility macros

Subject: [boost] [config] Major upgrade to Boost.Config symbol visibility macros
From: Beman Dawes (bdawes_at_[hidden])
Date: 2010-05-22 08:32:12

The upgrade to Boost.Config symbol visibility macros that has been
under discussion has been committed to trunk. This lays the groundwork
for resolving #2144, #2309, #3697.

See https://svn.boost.org/trac/boost/changeset/62140

Thanks Jürgen Hunold for his patches and much other work on symbol
visibility issues.

The changeset also applied the changes to Boost.System to act as a
testbed to ensure the changes are correct. That's a concern because
any breakage in Boost.Config could break a lot of other stuff. We also
want to get the Boost.Config changes right the first time as they kick
off rebuilds of everything that uses the config system.

The changes have been tested locally on Windows, Linux, and the Mac,
and Boost.Filesystem has been retested on those systems as a reality
check that unmodified user code continues to work.

As trunk regression tests cycle and our confidence builds, we will
start to suggest and/or apply changes to other libraries to make use
of the new facilities.

--Beman