Replace osc52yank.vim with autoload script

plugin/mappings.vim

@@ -95,8 +95,14 @@ nnoremap <leader>tm :tabmove<Space>
 " Clear search highlights
 nnoremap <leader><Space> :nohlsearch<CR>
 
-if exists('loaded_oscyank')
-  noremap <leader>y :Oscyank<CR>
+if tmux#isOption('set-clipboard', 'on') || $SSH_CONNECTION !=# ''
+  " When connected to a remote session the + selection register is not
+  " available and the unnamed register is used instead. Add mappings using the
+  " z register instead.
+  noremap <leader>y "zy
+  noremap <leader>Y "zY
+  " Enable OSC 52 copy on yank.
+  call osc52#autocmd()
 else
   " System clipboard yank/put
   noremap <leader>y "+y