message: Ensure we can always map for read even for non-persistent buffers
diff: @@ -490,9 +490,8 @@ void WrappedOpenGL::glNamedBufferStorageEXT(GLuint buffer, GLsizeiptr size, cons
  GLbitfield origflags = flags;
  - // if we're persistently writing, we want to be able to read as well, enable that.
  - uint32_t persistentWriteFlags = GL_MAP_PERSISTENT_BIT | GL_MAP_WRITE_BIT;
  - if((flags & persistentWriteFlags) == persistentWriteFlags)
  + // we always want to be able to read. This is true for persistent maps, as well as
  + // non-invalidating maps which we need to readback the current contents before the map.
  flags |= GL_MAP_READ_BIT;
  SERIALISE_TIME_CALL(GL.glNamedBufferStorageEXT(buffer, size, data, flags));
  @@ -527,9 +526,8 @@ void WrappedOpenGL::glBufferStorage(GLenum target, GLsizeiptr size, const void *
  GLbitfield origflags = flags;
  - // if we're persistently writing, we want to be able to read as well, enable that.
  - uint32_t persistentWriteFlags = GL_MAP_PERSISTENT_BIT | GL_MAP_WRITE_BIT;
  - if((flags & persistentWriteFlags) == persistentWriteFlags)
  + // we always want to be able to read. This is true for persistent maps, as well as
  + // non-invalidating maps which we need to readback the current contents before the map.
  flags |= GL_MAP_READ_BIT;
  SERIALISE_TIME_CALL(GL.glBufferStorage(target, size, data, flags));
  