This revision is intended as comparison point between the old and the new GC
The used GC can be switched in mmdisp and various statistics will be gathered during
execution (these will be removed/disabled in later revisions)
See the section `do notation` in the manual for more info.
* nkMacroStmt has been removed
Macro statements are now mapped to regular nkCall nodes.
The support for additional clauses (such as else, except, of, etc)
have been restored - they will now appear as additional arguments
for the nkCall node (as nkElse, nkExcept, etc nodes)
* fixed some regressions in the `is` operator and semCompiles
