Initialize the timer after the graphics device on desktop and web platforms. (#516)
This is already the order that is used for Android. It doesn't appear to
make a difference on desktop but on web using the timer before it's been
initialized (by glfwInit, inside InitGraphicsDevice) causes the a long
(and variable but often several seconds) sleep between the first and
second frame.
Fixes: 468309d ("Early-exit InitWindow if InitGraphicsDevice fails")