SkAtomics_sync.h included from src

[Bryce Harrington]

When installing skia, it should be possible to install all headers by effectively doing:

cp -r include/* /usr/include/skia

However, these include some header files which #include stuff from src, so it errors thusly when you try to actually build against it:

[ 2%] Building CXX object src/CMakeFiles/caskbench.dir/caskbench.cpp.o
In file included from /usr/include/skia/core/SkRefCnt.h:14:0,
from /usr/include/skia/core/SkFlattenable.h:13,
from /usr/include/skia/core/SkColorTable.h:14,
from /usr/include/skia/core/SkBitmap.h:12,
from /srv/Source/Caskbench/caskbench/src/caskbench.cpp:15:
/usr/include/skia/core/SkThread.h:52:31: fatal error: ../../src/ports/SkAtomics_sync.h: No such file or directory
#include SK_ATOMICS_PLATFORM_H
^
compilation terminated.

This can be worked around locally by doing:

define SK_ATOMICS_PLATFORM_H "ports/SkAtomics_sync.h"

define SK_MUTEX_PLATFORM_H "ports/SkMutex_pthread.h"

before including the skia header files.