Cleanup

Clean up code and documentation for glfwGetKeyScancode and add
implementation for Wayland and Mir.

Related to #830.

README.md

@@ -100,7 +100,7 @@ information on what to include when reporting a bug.
 ## Changelog
 
 - Added `glfwGetKeyScancode` function that allows retrieving platform depen-
-  dent scancodes for keys
+  dent scancodes for keys (#830)
 - Bugfix: Calling `glfwMaximizeWindow` on a full screen window was not ignored
 
 
@@ -222,6 +222,7 @@ skills.
  - Patrick Snape
  - Julian Squires
  - Johannes Stein
+ - Michael Stocker
  - Justin Stoecker
  - Elviss Strazdins
  - Nathan Sweet
@@ -245,7 +246,6 @@ skills.
  - Santi Zupancic
  - Jonas Ådahl
  - Lasse Öörni
- - Michael Stocker
  - All the unmentioned and anonymous contributors in the GLFW community, for bug
    reports, patches, feedback, testing and encouragement