Remove '-ffast-math' option.

Remove GCC 8.x check in Matrix3x4.h

CMake/Modules/UrhoCommon.cmake

@@ -620,8 +620,6 @@ else ()
                     set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -march=${URHO3D_DEPLOYMENT_TARGET}")
                 endif ()
             endif ()
-            set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -ffast-math")
-            set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -ffast-math")
             # We don't add these flags directly here for Xcode because we support Mach-O universal binary build
             # The compiler flags will be added later conditionally when the effective arch is i386 during build time (using XCODE_ATTRIBUTE target property)
             if (NOT XCODE)

Source/Urho3D/Math/Matrix3x4.h

@@ -149,7 +149,7 @@ public:
     /// Construct from translation, rotation and uniform scale.
     Matrix3x4(const Vector3& translation, const Quaternion& rotation, float scale) noexcept
     {
-#if defined(URHO3D_SSE) && (__clang__ || !defined(__GNUC__) || __GNUC__ < 8)
+#ifdef URHO3D_SSE
         __m128 t = _mm_set_ps(1.f, translation.z_, translation.y_, translation.x_);
         __m128 q = _mm_loadu_ps(&rotation.w_);
         __m128 s = _mm_set_ps(1.f, scale, scale, scale);
@@ -163,7 +163,7 @@ public:
     /// Construct from translation, rotation and nonuniform scale.
     Matrix3x4(const Vector3& translation, const Quaternion& rotation, const Vector3& scale) noexcept
     {
-#if defined(URHO3D_SSE) && (__clang__ || !defined(__GNUC__) || __GNUC__ < 8)
+#ifdef URHO3D_SSE
         __m128 t = _mm_set_ps(1.f, translation.z_, translation.y_, translation.x_);
         __m128 q = _mm_loadu_ps(&rotation.w_);
         __m128 s = _mm_set_ps(1.f, scale.z_, scale.y_, scale.x_);
@@ -686,7 +686,7 @@ public:
     /// Identity matrix.
     static const Matrix3x4 IDENTITY;
 
-#if defined(URHO3D_SSE) && (__clang__ || !defined(__GNUC__) || __GNUC__ < 8)
+#ifdef URHO3D_SSE
 private:
     /// \brief Sets this matrix from the given translation, rotation (as quaternion (w,x,y,z)), and nonuniform scale (x,y,z) parameters. Note: the w component of the scale parameter passed to this function must be 1.
     void inline SetFromTRS(__m128 t, __m128 q, __m128 s)