Each time the longest common substring is found the diff algorithm
recurses to reprocess the regions before and after the common string.
Large files with many edits can trigger StackOverflowError as the
algorithm attempts to process a deeply split tree of regions. This
is especially prone to happen in servers where the Java stack size
may have been limited to 1M or even 256K.
To keep edits produced in order a queue is used to process edits
in a depth-first strategy.
Change-Id: Iae7260c6934efdffac7c7bee4d3633a8208924f7
d11ca1b084