GL: make the usage parameter in Buffer::setData() optional.

So simple change, so big usability impact. These hints don't do much to
performance anyway.

doc/changelog.dox

@@ -73,6 +73,8 @@ See also:
 -   @ref GL::Mesh::draw() and @ref GL::MeshView::draw() now return a reference
     to self to make method-chained draws (for example using a different shader)
     possible as well
+-   The @ref GL::BufferUsage parameter in @ref GL::Buffer::setData() is now
+    optional, defaults to @ref GL::BufferUsage::StaticDraw
 
 @subsubsection changelog-latest-changes-meshtools MeshTools library
 

src/Magnum/GL/Buffer.h

@@ -1020,16 +1020,16 @@ class MAGNUM_GL_EXPORT Buffer: public AbstractObject {
          *      @fn_gl_extension_keyword{NamedBufferData,EXT,direct_state_access},
          *      eventually @fn_gl{BindBuffer} and @fn_gl_keyword{BufferData}
          */
-        Buffer& setData(Containers::ArrayView<const void> data, BufferUsage usage);
+        Buffer& setData(Containers::ArrayView<const void> data, BufferUsage usage = BufferUsage::StaticDraw);
 
         /** @overload */
-        template<class T> Buffer& setData(const std::vector<T>& data, BufferUsage usage) {
+        template<class T> Buffer& setData(const std::vector<T>& data, BufferUsage usage = BufferUsage::StaticDraw) {
             setData({data.data(), data.size()}, usage);
             return *this;
         }
 
         /** @overload */
-        template<std::size_t size, class T> Buffer& setData(const std::array<T, size>& data, BufferUsage usage) {
+        template<std::size_t size, class T> Buffer& setData(const std::array<T, size>& data, BufferUsage usage = BufferUsage::StaticDraw) {
             setData({data.data(), data.size()}, usage);
             return *this;
         }