bindgen shouldn't generate f32 for c floats

[jdm]

According to the conversation in gnzlbg/ctest#69 (comment), the fact that bindgen switched from generating c_float to f32 is a bug. I've encountered this in the harfbuzz bindings via https://github.com/servo/rust-harfbuzz/blob/d782b2c021978c615b870588555df80996dd39f7/harfbuzz-sys/harfbuzz/src/hb-font.h#L692.

[emilio]

@jdm curious, what platform are you on that has floats that aren't f32?

It's technically a bug, but not really something that I'd expect to come up with any sort of frequency.

[emilio]

What is the issue that you're hitting with harfbuzz? It's likely that's unrelated if you're in any sort of "common" platform.

[jdm]

@emilio I'm only paraphrasing the comments that I linked to. In this case, the presence of f32 broke ctest, which seems disinclined to add support for it.