libcore: rename vec::each(variable) to variable.each
librustdoc: rename vec::each(var) to var.each
libstd: rename vec::each(var) to var.each
libsyntax: rename vec::each(var) to var.each
librustc: rename vec::each(var) to var.each
auto merge of #6328 : recrack/rust/rename_cleanup, r=sanxiyn

rename vec::each(var) to var.each

> librustc, libsyntax, libstd, librustdoc, libcore