The GLFW context version hint is a minimum version, not maximum version so
requesting 4.4 and then falling back to lower versions doesn't make sense.
This change sets the minimum version to 3.2 and attempts to standardize this
across all example apps.
Also print the maximum supported GL version along with the context version
at startup.
We will need to find a solution for Ignacio's older setup, but this at least
fixes the other fallout.
* Use glewIsSupported instead of glewGetExtension
* Convert tabs to spaces
* Remove GLEW static caching (they only get called once)
As a preparation for retiring DrawContext, move SupportsAdaptiveTessellation
method to examples/common/glUtils, which is renamed and namespaced
from gl_common.{cpp,h} to be consistent to other files.
Same renamings applied to other example files.