Using imguiCollapse instead of imguiButton for imguiColorWheel.
Fixed drawText() to handle NULL or empty string.
Added imguiImageSwizzle().
Added imguiBorderButton().
Added imguiTabs().
Added optional _height param for imguiSeparator() and imguiSeparatorLine().
Fixing imgui scroll area scissoring.
Function setWindowTitle() now returns void.
Making setWindowTitle() on Windows thread safe.
Merge pull request #133 from dariomanesku/master

Imgui updates + setWindowTitle() fix.