Enable different copies of otherwise identical text renderers

Needed when using computeWidth() because it messes up draw() rendering.
Add text overlay textWidth() method

Is accessible from JavaScript.
Auto-size load URL and file menu items in editModels and newEditEntities

And fix a couple of typos.
fix bug with audio mixer muting too often
Merge pull request #3757 from PhilipRosedale/master

fix bug with audio mixer muting too often
Fix boolean literal value
fix a memory leak in OctreeElement
fix a leak in StdDev
rename StdDev to StDev, patch its leak
add destructors for arrays in Hair
include string.h for memset usage
include c++ header for memset
Merge pull request #3761 from birarda/plugs

fix a memory leak in OctreeElement, StDev
Fix build warning
Merge pull request #3759 from ctrlaltdavid/20140

CR for Job #20140 - Add Overlays.getTextWidth
Merge pull request #3762 from ctrlaltdavid/fix-build-warning

Fix build warning
Revert "Fix build warning"
Merge pull request #3763 from highfidelity/revert-3762-fix-build-warning

Revert "Fix build warning"
Revert "CR for Job #20140 - Add Overlays.getTextWidth"
Merge pull request #3764 from highfidelity/revert-3759-20140

Revert "CR for Job #20140 - Add Overlays.getTextWidth"