http://gcc.gnu.org/wiki/Visibility

<evoskuil> genjix, I have built all dependencies so that they can be
linked statically or dynamically, release or debug, 64 or 32 bit. The
packages include all variants...
<evoskuil> dynamic linking is platfrm-dependant and requires conditional
code for cross platform support....
* Coincidental (~coinciden@216.86.59.150) has joined #darkwallet
<evoskuil> all of our dependencies support dynamic and static linking, at
least on Windows...
<evoskuil> it would be nice to provide that option as well. it's a little
more complicated for c++ than for c...
<evoskuil>
http://www.codeproject.com/Articles/28969/HowTo-Export-C-classes-from-a-DLL

linux doesn't need this for shared libraries since g++ just exports all
symbols by default. but this is something i looked at before and it could
be worth doing, and if it's useful for msvc then we should do it.