fix 'safeNormalize' (probably should remove it)

Fix for Issue 953: cull degenerate triangles
https://github.com/bulletphysics/bullet3/issues/935
Thanks to Oleg Klimov for the report and reproduction case.

src/LinearMath/btVector3.h

@@ -291,14 +291,16 @@ public:
 
 	SIMD_FORCE_INLINE btVector3& safeNormalize() 
 	{
-		btVector3 absVec = this->absolute();
-		int maxIndex = absVec.maxAxis();
-		if (absVec[maxIndex]>0)
+		btScalar l2 = length2();
+		//triNormal.normalize();
+		if (l2 >= SIMD_EPSILON*SIMD_EPSILON)
 		{
-			*this /= absVec[maxIndex];
-			return *this /= length();
+			(*this) /= btSqrt(l2);
+		}
+		else
+		{
+			setValue(1, 0, 0);
 		}
-		setValue(1,0,0);
 		return *this;
 	}