ir: Handle _Complex _Float128 correctly.
ir: Handle _Complex _Float128 correctly.

Unfortunately we can't test it for the same alignment issues that "long double"
has.

Fixes #1087

rust-lang/rust-bindgen,emilio/rust-bindgen,emilio/rust-bindgen,emilio/rust-bindgen,emilio/rust-bindgen,rust-lang/rust-bindgen,emilio/rust-bindgen,rust-lang/rust-bindgen,rust-lang/rust-bindgen