auto merge of #5340 : brson/rust/column, r=brson

#5274
Remove unused variable
Remove unused import in core
Remove unused imports in std
Remove unused import in librustc
auto merge of #5336 : ILyoan/rust/remove_unused, r=sanxiyn

Remove unused imports to get rid of warnings.
librustc: Separate out trait storage from evec/estr storage
librustc: Don't accept `as Trait` anymore; fix all occurrences of it.
librustc: Remove overloaded operator autoderef.
librustc: Remove "base types" from the language.
librustc: Remove implicit self from the language, except for old-style drop blocks.
test: Some test fixes
librustc: Don't require the "static" keyword to define a static method
librustc: Allow path-qualified constants in patterns
test: Fix tests. rs=tests
libsyntax: Remove a use of deprecated Encodable from libsyntax. rs=burningtree
librustc: Remove another deprecated use of `as Trait`. rs=burningtree
core: Cleanup rt::context
Give core::rt and std::net their own uvll bindings

I intend to do some big refactoring and don't want to deal w/ std just now
core: Don't use printf in rtdebug!

The bots were showing a segfault that I can't reproduce. Assuming it's
varargs related so let's not use printf