Fixed case behaviour

* case no properly handles -h and --help flags, i.e. treats it as
  pattern
* fixed case escaping:
The following expressions now work correctly:
switch '*'
  echo '*'
  echo Match any string
end
switch '*'
  echo '\*'
  echo Match asterix
end
switch '\\'
  echo '\\\\'
  echo Match slash
end

The same for '?' sign

builtin.cpp

@@ -3838,7 +3838,7 @@ static int internal_help( const wchar_t *cmd )
 {
 	CHECK( cmd, 0 );
 	return contains( cmd, L"for", L"while", L"function",
-			 L"if", L"end", L"switch", L"count" );
+			 L"if", L"end", L"switch", L"case", L"count" );
 }