Fix serious error that graph label 2E10 was displayed as 2E1
Correct error in file dialog filter description
define GLintptrARB so that it's consistent with the prior def in openGL header
Merge branch '48'
add comments about xcode 5
another error shows up on OSX 10_9
improved virtualenv instructions + merge fixes in glext.h
Fix error in diff_angle when angle very small
Update Windows build instructions
Correct error in creating a display with scene.fullscreen = True
Fix bug that gcurve(pos=[(10,20), (50,30), (-5,-3)]) drew an extra line.
Remove scene.show_rendertime, which doesn't work in VPython 6 and isn't needed.
Fix two bugs in trails; don't add duplicate points, and detect ball.pos.x updates
Fix bug in curve(pos=[(0,0,0), (0,0,0), (1,0,0)], radius=0.1); eliminate initial duplicate points
Fix memory leak in curve and faces thru changes to primitives.py; very minor cleanups elsewhere
Check for a trailed object no longer existing, or trail not initialized
Fix bug in dot function (visua/numpy conflict); minor cleanup of old comments
Detect caps lock key state and use it when returning key inputs
Remove a debugging print statement
Restore a missing statement to visual_all.py