Sets default symbol visibility to hidden. Resolves #74

[jonesmz]

[BearishSun]

This fails on Windows because the thread-local stuff isn't allowed to be dll exported:

c:\projects\bsf\source\foundation\bsfutility\allocators\bsmemoryallocator.h(125): error C2492: 'bs::MemoryCounter::Frees': data with thread storage duration may not have dll interface (compiling source file C:\Projects\bsf\Source\Foundation\bsfCore\Scene\BsPrefab.cpp) [C:\Projects\bsf\Build\Source\Foundation\bsf.vcxproj]

[jonesmz]

Hrmm, so the difficulty here is that with gcc, unless I export the entire class, it won't link. Apparently they don't support exporting individual member functions.

Would you be OK with a conditional compile? Export the whole class with gcc, export only the functions with msvc ?

[BearishSun]

Yep, that sounds fine.

[jonesmz]

Sorry for the long delay on this issue. Busy with other stuff shrug. Still planning to provide a patch as described.