32-bit armv7 build fails

[Taylor Trump]

I hadn't tried before but maybe this issue is related to the latest commits?

Building with 1.5.0 nightly on armv7 fails:

Compiling wtftw_xlib v0.4.0 (file:///tmp/wtftw-master)
xlib/src/xlib_window_system.rs:97:42: 97:55 error: mismatched types:
 expected `*mut u64`,
    found `&mut u32`
(expected u64,
    found u32) [E0308]
xlib/src/xlib_window_system.rs:97             let root_ptr : *mut Window = &mut root_cpy;

[...]

error: aborting due to 22 previous errors 

which looks similar to this issue:

ogham/exa#83

[Simon Wollwage]

This has to do with the same issues mentioned in #75