android/skin/window.c: Remove dependencies.

This remove dependencies from android/skin/window.c to the
following headers:
   android/hw-sensors.h
   android/user-events.h
   android/opengles.h

+ Provide a proper declaration for setenv() on Windows, since it
  is implemented by android/utils/setenv.c already.

Note that after this patch, the content of android/skin/ only
depends on the android/utils/, and SDL, which should make it
easier to test / maintain / port in the long run.

Change-Id: I9df1f9d3af6c7ff716b2b6bfe6bb5d77f94f834f
android/skin/file.h: Remove SkinCharmapFuncs

Since all charmap/keycode sources were moved to android/skin/
it's no longer necessary to abstract the button name translation
to the client, so move it back into android/skin/file.c to simplify
android/qemulator.c a little bit.

Change-Id: I2de27023fb69c6fc849766ea6c561ceca0be42b5
Merge changes I2de27023,I9df1f9d3

* changes:
  android/skin/file.h: Remove SkinCharmapFuncs
  android/skin/window.c: Remove dependencies.