implement stub for OpenGL SalGraphicsImpl sub class

Change-Id: I8267bd26e1542230b9c112d741bba68d541b3994
it is false and not FALSE

Change-Id: I63c0cf97376d2aa4e27bed3e731b82af51b86804
use Impl for windows backend

Change-Id: Ie354aaf11644122754b69bc303c781297cacdc77