Add sqrt() and rsqrt() to Sk4f.

src/core/Sk4x_sse.h

Index: src/core/Sk4x_sse.h
diff --git a/src/core/Sk4x_sse.h b/src/core/Sk4x_sse.h
index ee09f774493946c29d55a019658df484ee7d6ccd..6077d0273d19d0244559c1fed93f381d290de086 100644
--- a/src/core/Sk4x_sse.h
+++ b/src/core/Sk4x_sse.h
@@ -99,6 +99,9 @@ M(Sk4f) subtract(const Sk4f& o) const { return _mm_sub_ps(fVec, o.fVec); }
 M(Sk4f) multiply(const Sk4f& o) const { return _mm_mul_ps(fVec, o.fVec); }
 M(Sk4f) divide  (const Sk4f& o) const { return _mm_div_ps(fVec, o.fVec); }
 
+M(Sk4f) rsqrt() const { return _mm_rsqrt_ps(fVec); }
+M(Sk4f)  sqrt() const { return _mm_sqrt_ps( fVec); }
+
 M(Sk4i) equal           (const Sk4f& o) const { return _mm_cmpeq_ps (fVec, o.fVec); }
 M(Sk4i) notEqual        (const Sk4f& o) const { return _mm_cmpneq_ps(fVec, o.fVec); }
 M(Sk4i) lessThan        (const Sk4f& o) const { return _mm_cmplt_ps (fVec, o.fVec); }