BAffineTransform: C++11 compatibility fix

inline const floats are a gcc extension. It is possible to do it in a
standard way in C++11 using constexpr, but then gcc will reject the
previously accepted nonstandard syntax.

headers/os/interface/AffineTransform.h

@@ -33,7 +33,11 @@
 class BAffineTransform : public BFlattenable {
 public:
 
+#if __cplusplus < 201103L
 	static	const double			kDefaultEpsilon = 1e-14;
+#else
+	static	constexpr double		kDefaultEpsilon = 1e-14;
+#endif
 
 public:
 									BAffineTransform();