Fix clang compiler warnings

Adds link of the Metal port.

I just implmeneted the native Metal port of NanoVG. ;)

Fixed return value of nvgText to be the position after the rendered
string, also fixed scaling of the value.

Allows to turn on/off antialias for shapes.

This commit adds a new `nvgShapeAntiAlias()` function for turning on/off antialias for specific shapes.

Prevents uploading unused vertices to GPU.

This commit fixes the bug that `glnvg__renderFill()` allocates unused quad vertices for `GLNVG_CONVEXFILL`, which causes unused vertices uploaded to the GPU.

Besides, the quad for the `GLNVG_FILL` type is changed to drawn by `GL_TRIANGLE_STRIP` instead of `GL_TRIANGLES` so two more vertices can be reduced per quad.

In one of my test case, I need to paste an image to a framebuffer about 5,000 times, and this change would reduce the total number of uploaded vertices from `52,106` to `22,476`. It is good for FPS and battery consumption.

Discards fragments as early as possible.

This commit moves the `discard` instruction in the fragment shader to an earlier position to avoid performing calculations whose results are unused.

Highlighted the need for render target stencil buffer.

Fixes how glext header is included.

This commit fixes the issue caused by #357 that nanovg failed to compile on iOS due to the wrong way of including glext header.

Bug fixes to compile under OS X 12.3

To make the examples link correctly under OS X 12.3, you need to include
<OpenGL/glext.h> in the file.  This commit limits what happens by protecting
the include as follows:

    #ifdef __APPLE__
    #   include <OpenGL/glext.h>
    #endif

Thus, this should have no effect on non-Apple systems.

To get nanovg to link correctly under OS X 12.3, it needs to be linked against
the Carbon libraries.  This was missing in the premake4.lua files.  Now fixed.

Improve nvgGlobalCompositeOperation with state

Add image flag to support GL_NEAREST rendering

suppresses all warnings reported by latest Xcode/AppleClang

Better support for CJK characters.

Previously, the Unicode range of the CJK chractaters only includes Chinese charactaters, Japanese Kanji, and CJK Symbols and Punctuation. The range are used by traditioanl Korean as well. This commit further includes Hiragana and Katakana in Japanese, and Hangul Syllables and Hangul Jamo in Korean to make CJK support more complete.

Fixes the bug that text may not render correctly.

This commit fixes the bug that text may not render correctly when glyph is not found in fallback fonts.

Improves to display CJK characters with English words.

This commit improves to display CJK characters mixed with English words so there is less spaces at line breaks.

Fixes line breaks for CJK characters.

handle file IO error

This commit fixes weird line breaks when rendering CJK (Chinese, Japanese, Korean) characters. Each CJK character is more like a word instead of a letter. This commit fixes the logic of line breaks by introducing a new `NVG_CJK_CHAR` code point type and takes special care for formatting text including CJK characters.

nvgRoundedRectEx for varying corner radii

Conflicts:
	src/nanovg.h

Fixes a bug when applying `NVG_IMAGE_FLIPY`.

This commit fixes issue #167 that `nvgImagePattern()` does not handle coordinate well if the specified image applies the `NVG_IMAGE_FLIPY` parameter.

Rename nvglImageFromHandleGL2 -> nvglImageHandleGL2

There was no nvglImageFromHandleGL2 implementation, it must have been
an error during some refactoring

Fallbacks to default composite operation when invalid one is specified.