arm: dynamic NEON support for SkBitmapProcState functions.

arm: dynamic NEON support for SkBitmapProcState functions.

This patch does the following:

  - Move the NEON-specific code from src/core/SkBitmapProcState_filter.h
    to src/opts/SkBitmapProcState_filter_neon.h

  - Implement the NEON-specific functions in the new source file
    src/opts/SkBitmapProcState_opts_arm_neon.cpp, added to the "opts_neon"
    static library target. All functions now use the _neon suffix, even
    in full-NEON builds.

  - Move most of the content of src/core/SkBitmapProcState.cpp to a
    new header: src/core/SkBitmapProcState_procs.h

This header is included by two source files:

  src/core/SkBitmapProcState.cpp, to define the regular functions.
  src/opts/SkBitmapProcState_opts_arm_neon.cpp to define NEON ones.

This is to deal with the fact that all NEON functions now
use the _neon suffix, even in SK_ARM_NEON_IS_ALWAYS mode,
and to be able to include the same header twice in the
SK_ARM_NEON_IS_DYNAMIC case.
Review URL: https://codereview.appspot.com/6449117

git-svn-id: http://skia.googlecode.com/svn/trunk@5055 2bbb7eff-a529-9590-31e7-b0007b416f81