Fix FreeBSD ioctl request constants

[dcuddeback]

On FreeBSD ioctl() is defined as taking c_ulong as the request parameter:

fn ioctl(fd: c_int, request: c_ulong, ...) -> c_int

Constants meant to be passed as the request parameter were being defined as a mixture of c_uint and c_ulong, which can cause type errors. For example, the following program

extern crate libc;

fn main() {
    unsafe {
        libc::ioctl(1, libc::TIOCEXCL);
    }
}

results in a type error:

error[E0308]: mismatched types
 --> src/main.rs:5:24
  |
5 |         libc::ioctl(1, libc::TIOCEXCL);
  |                        ^^^^^^^^^^^^^^ expected u64, found u32

This commit changes ioctl request constants on FreeBSD to c_ulong, which fixes the compilation error in the above test program.

[rust-highfive]

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[dcuddeback]

Duplicate of #704. Sorry, I overlooked that there was an existing PR before opening this one.