- Renamed FPScounter to PerfGraph
- dump avg times at exit

- moved performance counter and drawing to separate file
- tweaks to performance drawing

- added NVG_NOTUSED to suppress unused param warnings
- fixed scissor anti-aliased border width when zoomed

- fixed off-by-one pixels from demo
- added device-pixel-ratio support (retina support)
- added nvgEndFrame()

- use nvgCreateGLES2() instead of nvgCreateGL2() when NANOVG_GLES2 is
specified (ditto for gl3)
- use GL_RED instead of GL_LUMINANCE in ES3

- added option to turn off AA fringe generation
- added examples which use no AA fringes and  MSAA

- merged GL ES2 and GL2 backends
- GL2 uses now same structure as GL3

- added milliseconds to fps counter
- smooth fps reading a bit more
- changed GL3 to uber shader

- set swap interval to 0 to better see performance
- draw convex shapes without stencil to speed things up
- improve vertex buffer upload for gl3

- moved demo stuff to separate file
- created two separate examples for gl2 and gl3
- initial stab at OGL 3.2 core profile back-end (currently twice as
slows as 2.0)
- API change: glBeginFrame() takes view witdth and height as input
- added FPS counter to demo