Line of sight looks strange on some devices

[EMaksymenko]

Samsung Exynos devices render line of sight with square artefacts.

Problem needs investigation.

[EMaksymenko]

Fixed in 63cdf39

Problem composed of two parts:

1. Depth texture should have explicit high precision specification on Mali devices. It is lowp by default there.
2. Depth texture value should be read from R/X vector component instead of Z.