Constant doc strings are not placed into the C header output

[jamesmunns]

Given the following input:

/// A reasonable approximation of PI
pub const PI: f32 = 3.14159;

The following output is generated

#define PI 3.14159

I would instead expect the following to be generated:

/**
 * A reasonable approximation of PI
 */
#define PI 3.14159

So far I have successfully generated docs for other types, but constants do not seem to have their documentation brought along.

[emilio]

It looks like this is just a plain oversight. In src/bindgen/ir/constant.rs, documentation is kept around but never actually used. Should be trivial to fix.

[arsing]

#471

[jamesmunns]

Thank you @arsing and @emilio!