Fixed required-features bench tests failing when compiled on stable rust.
Fixed required-features bench tests failing when compiled on stable rust.

tshepang/cargo,durka/cargo,eminence/cargo,tsurai/cargo,durka/cargo,tsurai/cargo,nipunn1313/cargo,nipunn1313/cargo,tshepang/cargo,rustyhorde/cargo,rust-lang/cargo,rustyhorde/cargo,rust-lang/cargo,tshepang/cargo,rust-lang/cargo,achanda/cargo,tsurai/cargo,vojtechkral/cargo,vojtechkral/cargo,rust-lang/cargo,eminence/cargo,achanda/cargo,achanda/cargo,tsurai/cargo,rustyhorde/cargo,eminence/cargo,tsurai/cargo,nipunn1313/cargo,rustyhorde/cargo,durka/cargo,vojtechkral/cargo,tshepang/cargo,nipunn1313/cargo,vojtechkral/cargo,eminence/cargo,durka/cargo,achanda/cargo