Fix mcsc paths and escaping for Windows

test/handler/test_mcsc_handler.vader

@@ -9,8 +9,25 @@ After:
   unlet! g:ale_cs_mcsc_source
   call ale#linter#Reset()
 
+Execute(The mcs handler should work with the default of the buffer's directory):
+  AssertEqual
+  \ [
+  \   {
+  \     'lnum': 12,
+  \     'col' : 29,
+  \     'text': '; expected',
+  \     'code': 'CS1001',
+  \     'type': 'E',
+  \     'filename': ale#path#Winify(expand('%:p:h') . '/Test.cs', 'add_drive'),
+  \   },
+  \ ],
+  \ ale_linters#cs#mcsc#Handle(347, [
+  \   'Test.cs(12,29): error CS1001: ; expected',
+  \   'Compilation failed: 2 error(s), 1 warnings',
+  \ ])
+
 Execute(The mcs handler should handle cannot find symbol errors):
-  let g:ale_cs_mcsc_source='/home/foo/project/bar'
+  let g:ale_cs_mcsc_source = '/home/foo/project/bar'
 
   AssertEqual
   \ [