Demo dinaries update

Update README.md

ListBox() changed signature of ListBox() to match Combo(). Still not very happy about not using const char** anymore. (#931)

Fixing error: declaration of ‘size’ shadows a member of 'this' [-Werror=shadow]

Demo: Console: More friendly to text color changes.

Version 1.53

Demo: BeginCombo() demo code

Moving window doesn't use accumulating MouseDelta so straying out of boundaries keeps moved window at the same spot.

Examples: DirectX10,DirectX11: Moved call to OMSetRenderTargets() in main loop so example code can integrate more nicely with other code.

Misc comments, removed duplicated IM_ARRAYSIZE macro in imgui_demo.cpp (it is now declared in imgui.h)

Examples: Vulkan: Tweak

Examples: Comments, synched some minor drift between examples + stronger suggestion to use StyleColorsDark().

Renamed the emblematic ShowTestWindow() function to ShowDemoWindow(). Kept redirection function (will obsolete).

Comments

Fixed incorrect IM_DELETE macro (9cda86d) (#1517, #484, #504)

ImVector: Revert 6172e93 actually problematic with our current use (because we don't construct the instances).

Internals: Missing IM_DELETE usage (#1517)

Internals: Added IM_NEW, IM_DELETE helper macros (#1517, #484, #504)

Fixed warning with Clang+MSVC using __int64 to define the helper ImU64 type (#1184)

Various zealous warning fixes (Clang).

Removed reliance on ImU64 type for the ImDrawList assert. (#1184)

ImVector: Spacing.

ImVector: insert() uses grow_capacity() - had inconsistent resize policy

ImVector: Added assignments and = operators + comments.

Examples: DirectX: Using IM_ARRAYSIZE()

Various zealous warning fixes (thanks Clang).

Examples: Added null_example/ which is helpful for quick testing on multiple compilers/settings without relyong on graphics library.

Columns: Made PixelsToOffsetNorm() properly symetrical to OffsetNormToPixels() (#125)

Columns: Fixed dragging when using a same of columns multiple times in the frame. (#125)

Drag and Drop: Disable tracking mouse button ownership when an external drag source is active, to make it easier to achieve drag and drop over multiple OS windows. (#143)