Add a GLSL test that compares a loop index to an uniform

Comparing a loop index to an uniform is useful in WebGL GLSL shaders,
since it can be used to work around the lack of while loops. Add a test
for this. The test is known to have failed on at least some older NVIDIA
Tegra drivers.
Merge pull request #388 from NVIDIA/compare-loop-index-test

Add a GLSL test that compares a loop index to an uniform
Increased tolerance in oes-standard-derivatives test from 2 to 5 on
request from Qualcomm.

This is essentially a bug fix and has therefore been applied to the
1.0.1, 1.0.2 and top-of-tree conformance suites.
Merge pull request #389 from kenrussell/standard-derivatives-tolerance

Increased tolerance in oes-standard-derivatives test from 2 to 5 on