GuiClipboard: Reinitialize clipboard provider
GuiClipboard: Reinitialize clipboard provider

When the clipboard provider is sourced it short circuits if it cannot
find a working clipboard - this behaviour is used internally by nvim to
check if the provider is available, by checking for
provider#clipboard#Call which is not defined if no clipboard is
available.

equalsraf/neovim-qt,equalsraf/neovim-qt,equalsraf/neovim-qt,equalsraf/neovim-qt