Fixed MyersDiff to be able to handle more than 100k

MyersDiff was crashing with ArrayIndexOutOfBoundsException when
diffing huge files. This was because the snake data (begin and
end position while processing chunks of the text) was sequeezed
into a single int. But with longer texts to diff these values
exceeded the range of java int values. It is fixed by squeezing
the two ints into a long and by adding the LongList helper
class.

Change-Id: Iacb9082e1b076e994d1486aa8e512342ad7432b3
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>