rustpkg: Remove #[allow(vecs_implicitly_copyable)]
compiletest: Remove #[allow(vecs_implicitly_copyable)]
syntax: Remove #[allow(vecs_implicitly_copyable)]
rusti: Remove #[allow(vecs_implicitly_copyable)]
Remove vecs_implicitly_copyable from the compiler
Fix test fallout from removing vecs_implicitly_copyable
auto merge of #6434 : alexcrichton/rust/less-implicit-vecs, r=bstrie

This closes #5204 and #6421.

This also removes the `vecs_implicitly_copyable` lint (although now reading #6421, this may not be desired?). If we want to leave it in, it at least removes it from the compiler.