SideBySide2: Disable blinking cursor

Some users are bothered by the cursor blinking in the review
pane. Instead of a blinking box that overlays a character use a
single character underline that does not blink. This is more "old
school vi" and can be less distruptive when reading code.

Change-Id: I3791bd472da2975288acfb1195959ec7e5f207bc
(cherry picked from commit e4bf42fa4a41ccc6d81a2a944e4756016ab51d56)