Examples: Organized header files to make available features more visible.

Merge branch 'master' into navigation

Examples: Using #include "imgui.h" instead of <imgui.h> appear correct-er as per standard? xcode+clang are very nitpicky there.

Nav: Examples: Glfw+GL3: Added basic gamepad mapping code when io.NavFlags & ImGuiNavFlags_EnableGamepad is set. (will iterate/tweak before spreading to other examples). (#787)

Nav: Examples: DirectX11, Glfw+GL3: Basic code to map keyboard inputs when io.NavFlags & ImGuiNavFlags_EnableKeyboard is set. (will iterate/tweak before spreading to other examples). (#787)

Examples: Simplified mouse wheel handling. (#1463)

Horizontal mouse wheel: renamed io.MouseHorizWheel to io.MouseWheelH. Reorganized the code in NewFrame(). Examples: Updated GLFW+GL and SDL+GL accordingly. (#1463)

Merge branch 'tseeker/20171127-feature-horiz-wheel' of https://github.com/tseeker/imgui into tseeker-tseeker/20171127-feature-horiz-wheel ...

# Conflicts:
#	examples/sdl_opengl2_example/imgui_impl_sdl_gl2.cpp
#	examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp

Added ImGuiKey_Insert for future use. Setup in all example bindings. (#1541)

Examples: OpenGL3+GLFW: Using 3.2 context + GLSL version 150 (#1466)

Examples: Using IM_OFFSETOF macro. + Comments

Examples: Comments about invalid mouse pos.

Horizontal mouse wheel support ...

This patch adds support for the horizontal mouse wheel in ImGui. It
affects windows that can be scrolled, as long as the Ctrl key is not
being pressed.

The scrolling speed has been set empirically so that it matches the
scrolling speed on the Firefox browser when the horizontal wheel is
used.

Internally, it adds a MouseHorizWheel to ImGuiIO, which is then used in
NewFrame to scroll the current window.

The SDL/GL2, SDL/GL3, GLFW/GL2 and GLFW/GL3 examples has been modified
to use it.

Examples: Added a bunch of comments/referencs related to io.WantCaptureMouse, io.WantCaptureKeyboard (#1262, #1237, #1219, #635, #1058, #1051, #912, #533, #703, #446, #459, #364, #213, #52, and more)

Examples: Comments to guide people unfamiliar with the librairies used.

Examples: GLFW+GL2/GL3: Minor tweaks, comments.

Nav/Examples: honoring the io.WantMoveMouse flag in most common examples (#323) ...

Missing support Vulkan (#549), Apple (#575, #247), SDL (#58, #356),
Allegro, Marmalade (#368, #375)

Examples: GL3: Comments, tweaks (#1145)

Merge branch 'master' of https://github.com/nlguillemot/imgui into nlguillemot-master

Backup polygon mode, draw with filled polygons, restore state, for clients running opengl with glPolygonMode. closes #798

IO: io.MousePos needs to be set to ImVec2(-FLT_MAX,-FLT_MAX) when mouse is unavailable/missing. Previously ImVec2(-1,-1) was enough but we'll now accept negative mouse coordinates.

Examples: OpenGL3+SDL: Fix types to uses GlEnum (#1147)

casting to GLint on init

save and restore sampler in GL 3 examples

fixes types

Fix blend func state save/restore ...

AFAIK there's no such enum as `GL_BLEND_SRC` or `GL_BLEND_DST` in OpenGL3 and OpenGL4.

Maybe they're left over from previous versions? They don't even seem to exist in OpenGL 2.1. In fact checking they were deprecated in OpenGL 1.5 (they exist in 1.3)

Examples: GLFW+GL3, SDL+GL3: Fixed modifying bound Texture0 (#1087, #1088, #1116)

Examples: GL3: Comments about gl3w (#880)

Minor const fixes for overzealous warnings (#883)

Added a void* user_data parameter to Clipboard function handlers. (#875)