Add libyuv to third party component

[riza]

We recommend libyuv which provides video scaling and conversion method.
However, currently we only support libyuv as a stand alone project, with these drawbacks:

• Following the recommended steps to build the library, it is required to also download chromium project which is large in size (approximately 10GB).
• Changes on the libyuv project might break the existing build configuration.

This ticket will add libyuv to the third party folder, use a specific version and include only the necessary source.

Below is the steps to build and use libyuv:

For GNU targets

1. By default, libyuv will always be built automatically. This automatic build can be disabled via configure script param --disable-libyuv or --disable-video, also it will not be built when ffmpeg swscale is detected.
2. if you want to use external libyuv, specify --with-external-libyuv and set header/library search paths via CFLAGS and LDFLAGS environment variables.

Additional step for iOS targets

1. Add third-party/lib/libyuv-[TARGET].a to application project in XCode.

For Visual Studio

1. libyuv will always be built automatically.
2. To enable libyuv, add this to your config_site.h:

   #define PJMEDIA_HAS_LIBYUV		1
   

[riza]

In 5354:

Re #1937: Add libyuv to Visual Studio 2005 and 2015 solution.

[riza]

In 5358:

Re #1937: Change project and folder name for consistency with existing third party library.

[riza]

In 5360:

Re #1937: Change the include header format, so that user can specify external library.

[nanang]

In 5361:

Re #1937: Added libyuv build configs for GNU build systems.

[nanang]

In 5362:

Re #1937: Fixed compile warnings because of duplicate lines in libyuv's Makefile.