Made static library build with -fPIC for Rust.

Fixes #199.

README.md

@@ -72,6 +72,8 @@ GLFW bundles a number of dependencies in the `deps/` directory.
  - Added *partial and experimental* support for Wayland
  - Changed the default of `GLFW_REFRESH_RATE` to `GLFW_DONT_CARE` to maintain
    the default behavior
+ - Changed static library to build as position independent code for easier use
+   from the Rust language
  - Bugfix: The debug context attribute was set from `GL_ARB_debug_output` even
            when a debug context had not been requested
  - Bugfix: The particles example was not linked against the threading library