Make Strategy_MakeWellFormed operate in place.
Previously, MakeWellFormed processed tokens and appended them onto an output
array, which was presumably immutable and inaccessible to Injectors. By
having MakeWellFormed operate directly on the input array, the strategy
saves memory and will also allow for a rewind implementation, as a unifying
the two arrays allows Injectors to easily determine an index behind them they'd
like to reset state to.
Signed-off-by: Edward Z. Yang <edwardzyang@thewritingpot.com>