Support renaming fields/types/functions to use Rust naming conventions

[fitzgen]

Turn this C struct

struct foo_bar {
    int bazBolly;
};

into

#[repr(C)]
struct FooBar {
    baz_bolly: std::os::raw::c_int,
}

We could use the heck crate.

The hard part will be dealing with name clashes correctly.

[crumblingstatue]

If #1097 is not feasible, it would also be nice to rustify enum variant names.

[pepyakin]

I think we already have a general problem with a name clashing.

First thing that comes in mind is:

echo 'struct foo { int pub; int pub_; };' | bindgen --no-layout-tests - -- -E

/* automatically generated by rust-bindgen */

#[repr(C)]
#[derive(Debug, Copy, Clone)]
pub struct foo {
    pub pub_: ::std::os::raw::c_int,
    pub pub_: ::std::os::raw::c_int,
}

[fitzgen]

I think we already have a general problem with a name clashing.

Yeah, it will only get more likely with renaming fields, however.