Removed syntastic and replaced it with ale

Read more here:
https://github.com/w0rp/ale

sources_non_forked/ale/ale_linters/cs/mcs.vim

@@ -0,0 +1,33 @@
+let g:ale_cs_mcs_options = get(g:, 'ale_cs_mcs_options', '')
+
+function! ale_linters#cs#mcs#GetCommand(buffer) abort
+    return 'mcs -unsafe --parse ' . ale#Var(a:buffer, 'cs_mcs_options') . ' %t'
+endfunction
+
+function! ale_linters#cs#mcs#Handle(buffer, lines) abort
+    " Look for lines like the following.
+    "
+    " Tests.cs(12,29): error CSXXXX: ; expected
+    let l:pattern = '^\v(.+\.cs)\((\d+),(\d+)\)\: ([^ ]+) ([^ ]+): (.+)$'
+    let l:output = []
+
+    for l:match in ale#util#GetMatches(a:lines, l:pattern)
+        call add(l:output, {
+        \   'lnum': l:match[2] + 0,
+        \   'col': l:match[3] + 0,
+        \   'type': l:match[4] is# 'error' ? 'E' : 'W',
+        \   'code': l:match[5],
+        \   'text': l:match[6],
+        \})
+    endfor
+
+    return l:output
+endfunction
+
+call ale#linter#Define('cs',{
+\   'name': 'mcs',
+\   'output_stream': 'stderr',
+\   'executable': 'mcs',
+\   'command_callback': 'ale_linters#cs#mcs#GetCommand',
+\   'callback': 'ale_linters#cs#mcs#Handle',
+\})