remove unused openbsd std::isfinite and std::signbit implementations

Source/wtf/MathExtras.h

Index: Source/wtf/MathExtras.h
diff --git a/Source/wtf/MathExtras.h b/Source/wtf/MathExtras.h
index 835f9c986cfa7d8829e5ab4fe7aed68869e1b9b5..087c235aba046f002ef2c740d2f8e46c91a718cc 100644
--- a/Source/wtf/MathExtras.h
+++ b/Source/wtf/MathExtras.h
@@ -53,21 +53,6 @@ const float piOverFourFloat = static_cast<float>(M_PI_4);
 const double twoPiDouble = piDouble * 2.0;
 const float twoPiFloat = piFloat * 2.0f;
 
-#if OS(OPENBSD)
-
-namespace std {
-
-#ifndef isfinite
-inline bool isfinite(double x) { return finite(x); }
-#endif
-#ifndef signbit
-inline bool signbit(double x) { struct ieee_double *p = (struct ieee_double *)&x; return p->dbl_sign; }
-#endif
-
-} // namespace std
-
-#endif
-
 #if OS(ANDROID) || COMPILER(MSVC)
 // ANDROID and MSVC's math.h does not currently supply log2 or log2f.
 inline double log2(double num)