demo: Change default overdraw threshold to 1%
demo: Change default overdraw threshold to 1%

Generally speaking overdraw optimizer is reasonably efficient at finding
clusters even with threshold=1.0; since ACMR is pretty important in some
passes, like shadow generation, where overdraw is not that meaningful,
1.01 (1%) penalty is a more sensible default.

zeux/meshoptimizer,zeux/meshoptimizer,zeux/meshoptimizer