src: cares_wrap: remove two unused variables
src: rename macros.py to notrace_macros.py

This incarnation of macros.py is only used to disable the (d)trace
macros. Rename it so it better reflects its purpose. A new macros.py
will be added in a follow-up commit.
tools: fix js2c macro expansion bug

If the same macro was used twice in close proximity, the second one
didn't get expanded.
lib: macro-ify type checks

Increases the grep factor. Makes it easier to harmonize type checks
across the code base.