Fix leaking non-public 'use' statements with glob imports
Fix leaking immediate children and types via glob imports
Fix implicit leaks of imports throughout libraries

Also touch up use of 'pub' and move some tests around so the tested functions
don't have to be 'pub'
Change the default level of unused_imports to warn
Remove unused imports throughout src/
Add a special FIXME for subduing warnings in rpath.rs
Adding missing imports for tests, and gate off others