Fixes resulting from reviews by Alon, Chad, ChrisM
tmpnam and tmpfile fixes; fixes #2797 and #2798
text update
Integrate feedback to Runtime environment and OpenGL docs from ChrisM and Alon
Delete old optimising topic then move the valid one to top level.
Merge pull request #2799 from hamishwillee/incoming

Incoming - general docs updates
text update
split note in -O3 docs
Fixes to debugging topic (and related changes)
UPdates to Optimising code doc
Hide spammy stderr warning prints when doing a run of the browser test suite to attempt to debug buildbot problem http://trac.buildbot.net/ticket/2901
Merge pull request #2803 from juj/cleaner_browser_test_run

Cleaner browser test run
As per jP_wanN's comment, fix the CMake toolchain file find feature to never look at native system directories, but only look at CMAKE_FIND_ROOT_PATH.
Restore CMAKE_FIND_ROOT_PATH_MODE_PROGRAM to NEVER, since it is useful to find_program() for external system utilities.
Merge pull request #2802 from hamishwillee/incoming

Fixes to debugging topic (and related changes)
Integrate fixes to debugging and optimization topics from ChrisM and Alon
Add test suite doc and update everywhere to link to this. Update developers guide and associated docs
Fix a few broken links
fix regression from fcd39b851e52baf8f14dcc40a8e55058755a61b2 on not optimizing files when -c provided without an -o
Merge pull request #2804 from hamishwillee/incoming

Fixes to debugging, optimization, developers guide.