Fixes to allow clean 1-pixel thick lines in more use cases. PixelCenterOffset not the same as previously!

Minor text alignment

Added comments

Disable client state in OpenGL example after rendering. ...

Using the example code in another application that has other rendering
code can cause rendering bugs or memory access errors if client state
is not disabled.

Converted all Tabs to Spaces (git diff -w shows an empty diff)

Tidying up example applications so it looks easier to just grab code

Tweak MacOS X Makefile for likely scenario

Fixed scissoring in OpenGL example

OpenGL example now use the fixed function-pipeline. Code down by 120 lines.

Simplified ImDrawList system (samples are 20 lines shorter) + merged title bar draw bar.

Added Makefile for MacOS X (courtesy of djoshea)

Renamed Makefile

add a quick and dirty makefile to build on linux

Portability fixes to OpenGL example application (courtesy of djoshea)