Conformance test for glsl array of structs with first pos int or bool.

At the time of writing, in Mac OS X with some NVIDIA cards, reading an array of
structs using a loop variable where the struct has an int or bool as its first
member returns corrupted data.

This adds a test with three examples:
- struct with unused int in first position
- struct with unused bool in first position
- struct with used bool in first position

Screenshot of the test failing on a Mac on OS X 10.9.2 with an NVIDIA GT 650M:

![failing_osx_nvidia_gt_650m](https://cloud.githubusercontent.com/assets/21303/2794655/657bbe9c-cbef-11e3-84b1-1a6257892da0.png)

Screenshot of the same test on the same machine, but in Ubuntu:

![passing_linux_nvidia_gt_650m](https://cloud.githubusercontent.com/assets/21303/2794660/7f316b7a-cbef-11e3-82ae-a2cc4b0b0439.png)

Original report and discussion [here](https://code.google.com/p/chromium/issues/detail?id=365519).