Clean up bionic_macros.h a bit.

Use <android-base/macros.h> instead where possible, and move the bionic
macros out of the way of the libbase ones. Yes, there are folks who manage
to end up with both included at once (thanks OpenGL!), and cleaning that
up doesn't seem nearly as practical as just making this change.

Bug: N/A
Test: builds
Change-Id: I23fc544f39d5addf81dc61471771a5438778895b