Insert: Do not move end of line on open line (o/O)

Change the logic of open line commands so that if a selection lies
on the end of line character of the line from which we open a new
line, that selection does not move.

If we have two clients, A and B, with B's cursor on the eol character
of line L, and A hits `o` while on line L, B's cursor should stay
on the same (logical) line. Previous behaviour would make B's cursor
jump on the newly inserted line.

1 files changed, 1 insertions, 0 deletions

diff --git a/test/normal/open-multiple-above/in b/test/normal/open-multiple-above/in
new file mode 100644
index 00000000..257cc564
--- /dev/null
+++ b/test/normal/open-multiple-above/in
@@ -0,0 +1 @@
+foo