unhardcoding macro compilation, steps III and IV: engine and bundles
JIT: refactors importers
JIT: factors out macro runtimes
JIT macro compiler

Allows using macro implementations in the same compilation unit that
defines them if you enable -Xmacro-jit. Very-very experimental.
macro annotations, pre-alpha v2

unfortunately the original idea of hijacking enterSym didn't work
(see the comments in Namers.enterSym for more information), so I had
to resort to a very ugly hack, since I do need macro annots right away