click-buildtool internals: Print #include directives in a stable order.

Rather than in order of hash table inclusion, which isn't stable and
caused problems at Meraki for Jim Roewe and Cliff Frey.
Internal: Use a helper function to parse elementmaps for a package.
Improve click-mkmindriver performance with packages.

* Actually add package elements to the list of requirements.
* Use package() to determine which package an element is in, not
  some jankass crap.
* Also, -V reports which elementmaps were parsed.

Von Cliff complainert.