Update for latest rustc
Update for latest rustc

vec.as_imm_buf and str.as_imm_buf are no more. The replacement is
.as_ptr() and .len().

trevex/luajit-rs,tempbottle/rust-lua,green-panther/rust-lua,beatgammit/rust-lua,kballard/rust-lua,tempbottle/rust-lua,green-panther/rust-lua,beatgammit/rust-lua,kballard/rust-lua,trevex/luajit-rs