Examples: Fixed warnings for Clang

Examples: Added STB_IMAGE_STATIC in examples to avoid conflicting implementation. Relate to #109

New and better Set[Next]Window(Pos|Size|Collapsed) API. ...

Removed rarely useful SetNewWindowDefaultPos() in favor of new API.

OpenGL example: allow resizing window.

Fix Clang warning with offsetof() macro? Added -Wall in OpenGL 3 example.

Examples: DirectX11: moved shader to be close to its usage location,

Examples: OpenGL3: cleaned up to match features of OpenGL2 example

Examples: adding title to the top of each examples. Cleaning up file headers.

Example apps: accumulate mouse wheel to accodomate for slow framerate.

DirectX11 example: further tweaks/massaging (-15 lines). Syncing example.

Removed Microsoft IME handler in examples, too confusing. Moved to imgui.cpp instruction block.

Tab->Spaces :(

Added DirectX11 example application (code is too long!)

Example code: warning fix + comments.

Updated example code.

Moved IO.Font*** options to inside the IO.Font-> structure.. Added IO.FontGlobalScale setting (vs Font->Scale)

Renamed ImBitmapFont -> ImFont, removed abstraction-pretend typedef

Fixed compatibility with std::vector if user decide to #define ImVector

OpenGL example: uses offsetof() macros for vertice definition instead of hardcoded offsets

OpenGL example: made the render function save/restore OpenGL state properly-ish

OpenGL/DirextX examples: comments and tweaks.

OpenGL example: Tentative fix for missed tap-to-click events on MacBook trackpad

OpenGL example: minor tweak for non-default font.

OpenGL/DirectX examples: support for international text input in UTF-8 + implement ImeSetInputScreenPosFn on Windows.

OpenGL example: added commented code to load custom font from filesystem

OpenGL example: comments on glfw window size vs frame buffer size.

Add support for Retina displays on MacOSX.

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

Minor text alignment

Added comments