Re-enable blt_combine_static_libraries test on Windows

PR #179 disabled the ``SHARED`` variant of the ``blt_combine_static_libraries`` test on Windows due to a linker error.

@white238 noted that there is a known problem with this macro and that he is working on a fix. Once the ``combine_static_libraries`` macro is fixed, we should re-enable this test in our Windows configurations.

Start by reviewing PR #179 and the blt_combine_static_libraries macro, then reproduce the linker error in the Windows configuration. Investigate the known macro problem and re-enable the SHARED variant of the blt_combine_static_libraries test once the Windows configuration passes.

Written by the indexing model from the issue text.