Add vec.rs each2_mut function
Add vec.rs each2_mut testsuite
auto merge of #6388 : recrack/rust/each2_mut, r=pcwalton

- vec.rs :add 'each2_mut function'
- testsuit : run-pass/vec-each2_mut.rs
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