Use __declspec to support windows shared libraries

[alanlivio]

Today, all binaries (i.e. ginga, gingagui, tests) are compiled staticly and make slow de development on windows environment. We may use nclua[1] MACROS.

[1] https://github.com/TeleMidia/nclua/blob/53d9277a7efa6c316e13bfe0b5bc60f2d4c3aef8/lib/ncluaconf.h.in

[robertogerson]

Do we need it for the "Refactoring Release"?

[alanlivio]

You right, its not high priority. But its good to be done in future.