Remove bulk float <-> half routines. These are dead code.

src/core/SkOpts.h

Index: src/core/SkOpts.h
diff --git a/src/core/SkOpts.h b/src/core/SkOpts.h
index f551bf453c385e1aa09e7a700ad3d2c2ac1ccd22..2bf4bdabde47de1f51a2c537d3294c13c127e35f 100644
--- a/src/core/SkOpts.h
+++ b/src/core/SkOpts.h
@@ -62,9 +62,6 @@ namespace SkOpts {
                         inverted_CMYK_to_RGB1, // i.e. convert color space
                         inverted_CMYK_to_BGR1; // i.e. convert color space
 
-    extern void (*half_to_float)(float[], const uint16_t[], int);
-    extern void (*float_to_half)(uint16_t[], const float[], int);
-
     // Blend ndst src pixels over dst, where both src and dst point to sRGB pixels (RGBA or BGRA).
     // If nsrc < ndst, we loop over src to create a pattern.
     extern void (*srcover_srgb_srgb)(uint32_t* dst, const uint32_t* src, int ndst, int nsrc);