Compiling on rust 1.4 fails

[chwevans]

Building master as of today fails on rust 1.4.

$ cargo build
   Compiling pistoncore-glfw_window v0.12.0 (file:///Users/chase/Documents/rust_projects/glfw_window)
src/lib.rs:108:27: 108:53 error: mismatched types:
 expected `*const libc::types::common::c95::c_void`,
    found `*const libc::c_void`
(expected enum `libc::types::common::c95::c_void`,
    found enum `libc::c_void`) [E0308]
src/lib.rs:108         gl::load_with(|s| window.get_proc_address(s));
                                         ^~~~~~~~~~~~~~~~~~~~~~~~~~
src/lib.rs:108:27: 108:53 help: run `rustc --explain E0308` to see a detailed explanation
src/lib.rs:264:9: 264:48 error: mismatched types:
 expected `*const libc::types::common::c95::c_void`,
    found `*const libc::c_void`
(expected enum `libc::types::common::c95::c_void`,
    found enum `libc::c_void`) [E0308]
src/lib.rs:264         self.window.get_proc_address(proc_name)
                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/lib.rs:264:9: 264:48 help: run `rustc --explain E0308` to see a detailed explanation
error: aborting due to 2 previous errors
Could not compile `pistoncore-glfw_window`.

To learn more, run the command again with --verbose.

[bvssvni]

This is probably because of a breaking change in libc. See PistonDevelopers/eco#98