Missing examples changelog bits and todo list

Examples: OpenGL3: Removed unnecessary backup/restore of GL_ELEMENT_ARRAY_BUFFER_BINDING since this is part of the VAO state. (#1836)

Examples: Comments about GLSL version not being the same as GL context version. (#1828)

Examples: GLFW: Made it possible to Shutdown/Init the backend again (by reseting the time storage properly). Changelog. Added to Vulkan example. (#1827)

Examples: GLFW* Make subsequent window creation possible.

Examples: OpenGL3: Trying to make the call to glBindSampler optional to make the example code easier to use/share with different context version. (#1806)

Added IMGUI_CHECKVERSION() macro to compare version string and data structure sizes in order to catch issues with mismatching compilation unit settings. (#1695, #1769)

Fix typos KeyDown => KeysDown

Examples: Added missing calls for ::DestroyWindow, glfwDestroyWindow() + fix old comments.

Renamed ImGuiConfigFlags_NoSetMouseCursor to ImGuiConfigFlags_NoMouseCursorChange. Followup to 75c3793 two weeks ago. (#787, #1495, #1202) + comments

Examples: GLFW: Don't alter cursor mode if GLFW_CURSOR input mode is GLFW_CURSOR_DISABLED. (#1202) [@PhilCK]

IO: Added ImGuiConfigFlags_NoSetMouseCursors. Added ImGuiBackendFlags_HasMouseCursors, ImGuiBackendFlags_HasSetMousePos. (#787, #1495, #1202)

Added ImGuiBackendFlags for backend to expose its capabilities. Added ImGuiBackendFlags_HasGamepad. (#787, #1542)

IO: Renamed io.WantMoveMouse to io.WantSetMousePos (was added in 1.52, _not_ used by core and only honored by some binding ahead of merging the Nav branch) + internal renaming (#787)

Examples: Renamed applications to emphasis on use of GLFW as a platform framework + minor local tweaks

Examples: Renamed glfw error callback for clarity.

Examples: OpenGL3: Added a way to override the glsl version number through the Init call. (#1667, #1466)

Renamed ImGuiStyleVar_Count_ to ImGuiStyleVar_COUNT for consistency with other enums. Added

Do not store compiled objects outside the project tree.

Define SOURCES instead of OBJS in Makefiles. ...

OBJS is still deduced from SOURCES, but this change gives better control
over where the object files get actually written.

Use make variables $@ and $^ where appropriate.

Ensure `make clean` is idempotent. ...

Prior to this, `make clean` would fail if the project was not already
fully built, and a second invokation would always fail.

Renamed ImGuiNavFlags io.NavFlags to ImGuiConfigFlags io.ConfigFlags. (#787)

Examples: Fix d749d49 missing the deletion code. (#1217)

Examples: OpenGL3: Create the VAO in the render function so the setup can more easily be used with multiple shared GL context. (#1217)

Examples: OpenGL: Cast call to glPolygonMode(). (#1628).

Examples: Mouse cursor handling comments/tweaks to homogenize. (#1495)

Examples: GLFW: Added support for mouse cursors (ImGui::GetMouseCursor() value and WM_SETCURSOR message handling). (#1495)

Examples: GLFW*: Renamed GLFW callbacks exposed in .h to not include GL2/GL3/Vulkan in their name.

Examples: GLFW+GL2/GL3: Added glPixelStorei() calls borrowed from SDL examples.