Update generator to latest rustc
Upgrade to latest rust (DANGEROUS)

Closes https://github.com/bjz/gl-rs/issues/76

Notice the transmute is replaced by direct casting by pointers. I do
not know how this affects the usage of the library. I left the ‘unused
import’ warning on in case this can be fixed later. If this is
critical, I would recommend doing an analysis and document which uses
cases one should be careful.

Conflicts:
	src/gen/main.rs
Update to latest glfw-rs
Fix unused import warning
Merge pull request #78 from bjz/rustc-update

Rustc update
Modified Makefile to work with Mingw

Applied changes by @imbaczek