Include modified B side lines when whitespace is ignored

SideBySide2 needs the modified B side lines even if the lines are
"common" when compared to A using the selected whitespace ignore
option. The modified B lines must be used so the text aligns properly
with surrounding context, such as wrapping some unmodified code in
an if block.

Send these by splitting an "ab" block into "a, b, common:true",
allowing the UI to correctly reconstruct the B side.

Change-Id: I5e045c32d9e86434094e03e844fb80ef4186993f
5 files changed