testsuite: Update and un-xfail #3601 test
Turn old `drop` blocks into `Drop` traits
Remove the last remnants of rtcalls
auto merge of #5152 : catamorphism/rust/issue-3601, r=catamorphism
auto merge of #5155 : bstrie/rust/dedrop, r=pcwalton

This removes all but 6 uses of `drop {}` from the entire codebase. Removing any of the remaining uses causes various non-trivial bugs; I'll start reporting them once this gets merged.
auto merge of #5159 : brson/rust/rtcall, r=brson
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'