more accurate cursor for message list

[nturner]

When the pointer is over the message list, the cursor is a hand. This indicates that a single click will take you somewhere. This patch changes the cursor for the message list to the default arrow cursor, which indicates that a single click will select the item under the pointer, and that a double click will activate it. This is more in line with how RoundCube actually behaves.

[nturner]

patch against r843

[seansan]

Review and decide in 0.1.1

[till]

@alec [x] yes [ ] no

[alec]

Applied in r1689.