Move highlight autocmds from plugin/ to ftplugin/

This results in simpler code (we don't need all the compatibility
checks) and faster launch for vim, as the highlighting autocmds are not
created until a .cs file is opened.

Author: nickspoons

autoload/OmniSharp/util.vim

@@ -123,8 +123,6 @@ function! OmniSharp#util#CheckCapabilities() abort
   endif
 
   if !s:capable
-    " Clear BufEnter and InsertLeave autocmds
-    silent! autocmd! OmniSharp_HighlightTypes
     " Clear plugin integration autocmds
     silent! autocmd! OmniSharp_Integrations
   endif

ftplugin/cs/OmniSharp.vim

@@ -3,26 +3,43 @@ if !OmniSharp#util#CheckCapabilities() | finish | endif
 if get(b:, 'OmniSharp_ftplugin_loaded', 0) | finish | endif
 let b:OmniSharp_ftplugin_loaded = 1
 
+if get(g:, 'OmniSharp_start_server', 0)
+  call OmniSharp#StartServerIfNotRunning()
+endif
+
+call OmniSharp#actions#buffer#Update()
+if g:OmniSharp_highlighting
+  call OmniSharp#actions#highlight#Buffer()
+endif
+
 augroup OmniSharp_FileType
   autocmd! * <buffer>
 
-  autocmd BufLeave <buffer>
+  autocmd BufEnter,BufLeave <buffer>
   \ if !pumvisible() |
   \   call OmniSharp#actions#buffer#Update() |
   \ endif
 
   autocmd CompleteDone <buffer> call OmniSharp#actions#complete#ExpandSnippet()
 
   autocmd TextChanged <buffer> call OmniSharp#actions#buffer#Update()
-augroup END
 
-setlocal omnifunc=OmniSharp#Complete
+  if g:OmniSharp_highlighting
+    autocmd BufEnter <buffer> call OmniSharp#actions#highlight#Buffer()
+  endif
+  if g:OmniSharp_highlighting >= 2
+    autocmd InsertLeave,TextChanged <buffer> call OmniSharp#actions#highlight#Buffer()
+  endif
+  if g:OmniSharp_highlighting >= 3
+    autocmd TextChangedI <buffer> call OmniSharp#actions#highlight#Buffer()
+    if exists('##TextChangedP')
+      autocmd TextChangedP <buffer> call OmniSharp#actions#highlight#Buffer()
+    endif
+  endif
 
-if get(g:, 'OmniSharp_start_server', 0)
-  call OmniSharp#StartServerIfNotRunning()
-endif
+augroup END
 
-call OmniSharp#actions#buffer#Update()
+setlocal omnifunc=OmniSharp#Complete
 
 command! -buffer -bar OmniSharpRestartAllServers call OmniSharp#RestartAllServers()
 command! -buffer -bar OmniSharpRestartServer call OmniSharp#RestartServer()

plugin/OmniSharp.vim

@@ -50,39 +50,8 @@ command! -bar -nargs=? OmniSharpInstall call OmniSharp#Install(<f-args>)
 command! -bar -nargs=? OmniSharpOpenLog call OmniSharp#log#Open(<q-args>)
 command! -bar -bang OmniSharpStatus call OmniSharp#Status(<bang>0)
 
-" Initialise automatic type and interface highlighting
 " Preserve backwards compatibility with older version g:OmniSharp_highlight_types
 let g:OmniSharp_highlighting = get(g:, 'OmniSharp_highlighting', get(g:, 'OmniSharp_highlight_types', 2))
-if g:OmniSharp_highlighting
-  augroup OmniSharp_HighlightTypes
-    autocmd!
-    autocmd BufEnter *.cs,*.csx
-    \ if !pumvisible() && OmniSharp#util#CheckCapabilities() |
-    \   call OmniSharp#actions#highlight#Buffer() |
-    \ endif
-
-    if g:OmniSharp_highlighting >= 2
-      autocmd InsertLeave,TextChanged *.cs,*.csx
-      \ if OmniSharp#util#CheckCapabilities() |
-      \   call OmniSharp#actions#highlight#Buffer() |
-      \ endif
-    endif
-
-    if g:OmniSharp_highlighting >= 3
-      autocmd TextChangedI *.cs,*.csx
-      \ if OmniSharp#util#CheckCapabilities() |
-      \   call OmniSharp#actions#highlight#Buffer() |
-      \ endif
-
-      if exists('##TextChangedP')
-        autocmd TextChangedP *.cs,*.csx
-        \ if OmniSharp#util#CheckCapabilities() |
-        \   call OmniSharp#actions#highlight#Buffer() |
-        \ endif
-      endif
-    endif
-  augroup END
-endif
 
 function! s:ALEWantResults() abort
   if !g:OmniSharp_server_stdio | return | endif