- fixed flags setup in nvglCreateImageFromHandle
- changed frame buffer to only compile on GL3
- changed nvgluCreateFramebuffer() to return FBO struct instead of
filling existing one (for consistency)

- added documentation about changed GL state
- made old GL2 and GL3 backends obsolete

- made uniform buffer support behind separate define for easier toggling
- calculate scissor and stroke alpha outside type selection to simplify
the shader (or else it produces rendering artefacts)
- restore default pixel store settings instead of restoring old state
- set active texture to 0 when starting to render a frame

- added support for GL(ES)2 for nanovg_gl3buf (something is still not
quite there)
- nanovg now sets all required GL state
- removed compiler warnings about unused vars

- added support to take screen shots
- added support to render to frame buffer using premultiplied alpha
- fixed spelling NVGaling -> NVGalign

- 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()

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

- 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