Also affect other popups which called FindBestPopupWindowPos() on their
second frame but it most often acts as a no-op but it wouldn't be
noticeable.

Scrollbar: background color less translucent in default style (flattened alpha) so it works better on non-WindowBg colored background.

InputText: removed the need for text_end pointer in the cursor position calculation loop, allows switching buffers

InputText: added comments and somehow clarified the optimized code that calculate text position + updated demo

Examples: Added example app for the Marmalade platform.

Examples: DirectX11: Fix vertex POSITION format (ImDrawVert::pos is 2D, not 4D)

the inputlayout incorrectly described the POSITION attribute as being
4D, while ImDrawVert::pos is 2D. This went unnoticed because the buffer
binding has a stride of sizeof(ImDrawVert) and the POSITION is treated
as a float2 in the vertex shader. If you switch POSITION to float4 in
the vertex shader (and actually use the z/w in the matrix
multiplication) then everything become wacky-looking since it's
interpreting the texture coordinates as z/w. On a similar note: It's
weird that the projection matrix takes z and w into consideration when
those don't exist in the shader due to positions being float2s.

InputText: Fix for not being able to enter certain characters in InputText on german keyboard

Fix for AltGR being send as Ctrl&Alt on german keyboards. Don't consume characters if CTRL key press is detected AND ALT key press is detected in Imgui::InputTextEx

Examples: OpenGL3: Add msys2/mingw64 target.

More begging, still in search for a solution..

Loosely related to #362