Do loops

Do loops should also always be parenthesised. Loop conditions should be listed one per line, starting after the opening parenthesis and indented one character. The `do' keyword should be at the end of the last condition. The body of the loop should then follow on the next line, again indented. Example:

(for(J, I + 1, N),
 param(A, I) do
        Diff is J - I,
        A[I] #\= A[J],
        A[I] #\= A[J] + Diff,
        A[I] #\= A[J] - Diff
).