refactored the generated decoder functions into the impl mod.
refactored the generated decoder functions into the impl mod.

lifthrasiir/rust-encoding,nox/rust-encoding,tempbottle/rust-encoding,tempbottle/rust-encoding,tempbottle/rust-encoding,nox/rust-encoding,lifthrasiir/rust-encoding,lifthrasiir/rust-encoding,nox/rust-encoding