Port SkTextureCompression opts to SkOpts

Pretty vanilla translation.  I cleaned up who calls whom a little.
Used to be utils -> opts -> utils, now it's just utils -> opts.

I may follow up with a pass over the NEON code for readability
and to clean up dead code.

This turns on NEON A8->R11EAC conversion for ARMv8.
Unit tests which now hit the NEON code still pass.
I can't find any related bench.

BUG=skia:4117

Review URL: https://codereview.chromium.org/1273103002
diff --git a/src/core/SkOpts.cpp b/src/core/SkOpts.cpp
index 86981b9..17eab7e 100644
--- a/src/core/SkOpts.cpp
+++ b/src/core/SkOpts.cpp
@@ -12,6 +12,7 @@
 #include "SkBlurImageFilter_opts.h"
 #include "SkFloatingPoint_opts.h"
 #include "SkMorphologyImageFilter_opts.h"
+#include "SkTextureCompressor_opts.h"
 #include "SkUtils_opts.h"
 #include "SkXfermode_opts.h"
 
@@ -46,6 +47,9 @@
     decltype( erode_x)  erode_x = portable::erode_x;
     decltype( erode_y)  erode_y = portable::erode_y;
 
+    decltype(texture_compressor)       texture_compressor = portable::texture_compressor;
+    decltype(fill_block_dimensions) fill_block_dimensions = portable::fill_block_dimensions;
+
     // Each Init_foo() is defined in src/opts/SkOpts_foo.cpp.
     void Init_sse2();
     void Init_ssse3();