Vulkan backend: g_FrameIndex not used fix -> huge perf gain ...

Added a macro to switch between unlimited frame rate (VK_PRESENT_MODE_IMMEDIATE_KHR) and limited to 60 fps (VK_PRESENT_MODE_FIFO_KHR). Only the latter mode is guaranteed to be available, but the former one most likely is.

Fix scissor offset being negative

Fix new Vulkan validation warnings

Examples: Speculative fix for OSX Makefile to make Travis happy (re #812)

Examples: DirectX9: Explicitely setting viewport to match that other examples are doing (#937)

Examples: Vulkan: Coding style fixes (#910)

Vulkan example: Proper surface format search.

Vulkan example: Fix gamma for some implementations.

Vulkan example: Fix validation layer warnings and errors and redeclare gl_PerVertex.

Examples: DirectX9-10-11: Only call Windows' SetCursor(NULL) when io.MouseDrawCursor is set (#585, #909)

Examples: Vulkan: Shallow stylistic changes (following #879)

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

Examples: GL3: Comments about gl3w (#880)

Fixed overzealous GCC warnings (#883) + partly undo 8553bab

Merge pull request #898 from tinnnysu/master ...

Examples: SDL+OpenGL2: Update cmdline syntax in Windows compilation.

Minor const fixes for overzealous warnings (#883)

update cmdline syntax in windows compilation

Add location decorators & change to use structs as in/out in glsl, update embedded spv (produced with glslangValidator -x)

Null the released resources

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

Examples: GLFW+OpenGL3: Fixed Shutdown() calling GL functions with NULL parameters if NewFrame was never called (#800)

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

Fixing minor english typos (#827)

Examples: OpenGL2: Uploading font texture as RGBA32 to increase compatibility with users shaders for beginners (#824)

Fix Mac OS X build and remove cruft from Makefile

Examples: OpenGL*: Savnig/restoring existing scissor rectangle for completeness (#807)

Examples: OpenGL3: Revert Makefile change for OSX for now (#812)

Examples: Accessing ImVector fields directly, feel less stl-ey and fix renderer side assert when render list only contains a callback (#810)

Correct name for linking opengl3_example ...

According to glfw offcial site, linking `libglfw.3.dylib` etc should
use `-lglfw`.

Changed this made the compilation on my Mac successfully.

fixed space issues