Fix warning about unused function helper_quadratic_to(). 

Only comment function if needed in the future.
Fix format not a string literal and no format arguments [-Wformat-security].

Fix identical to 957aeec81bc6c7da9a1b8c727c8b9d2ed278f4dc
Fix Warning about unsed variable. currentNormal was orphaned in a2b95e9.
Examples: Fix comparison to unsigned warnings (-Wsign-compare).
Addons: Fix comparison to unsigned warnings (-Wsign-compare).
Fix unused variable warnings (-Wunused-variable).
Examples: Fix various other warnings.
Linux examples scripts: Skip OSX-only examples.
Warnings: Correct some oversights.
Warnings: fix some stragglers.
glInfoExample: Fix file opening on Linux.
Merge branch 'develop' into fix-warnings

Conflicts:
	examples/addons/threadedImageLoaderExample/src/testApp.cpp
Merge pull request #1838 from bilderbuchi/fix-warnings

Fix lots of compile warnings