Don't use memset to initialise aggregate of floats.

In C3D_RENDER_OGL_LEGACY::setupMaterial(), the struct
m_materials (which is made up of floats and glm::vec3f's)
is initialised with a memset to 0. This is unsafe, as
floating point value representations in C++ are implementation-
defined (so 0 in memory is not 0-valued for sure).

Use empty-brace aggregate-initialisation, which does the right thing.

3d-viewer/3d_rendering/3d_render_ogl_legacy/c3d_render_ogl_legacy.cpp

@@ -175,8 +175,7 @@ void C3D_RENDER_OGL_LEGACY::render_3D_arrows()
 
 void C3D_RENDER_OGL_LEGACY::setupMaterials()
 {
-
-    memset( &m_materials, 0, sizeof( m_materials ) );
+    m_materials = {};
 
     if( m_settings.GetFlag( FL_USE_REALISTIC_MODE ) )
     {