Add versioning macros.

[drwells]

This commit adds basic preprocessor constants and one function for doing version checks. One can now do things like

#if IBAMR_VERSION_GTE(1, 0, 0)
    std::vector<MeshBase *> meshes;
#else
    std::vector<Mesh *> meshes;
#endif

for compatibility with the changes made in #368.

I really wish I had realized this was missing before the 0.3.0 release; better late than never, I suppose.

[drwells]

autoheader is trying to outsmart me... this doesn't work. I'll patch it in a few minutes.

[drwells]

That should work.

Jenkins retest this please