[9fans] libdraw apps sometimes die of SIGWINCH

[9fans] libdraw apps sometimes die of SIGWINCH

[Kris Maglione]

Immediately after the change to the devdraw process, I noticed that 
libdraw apps would die immediately if started in the framing mode of 
framing window managers, but not if started in floating mode and moved 
there later. Recently, the fact that my port of page died every time it 
was put into managed mode goaded me into finding the problem.

Page seems to be the only app to die whenever it receives SIGWINCH, but 
every other libdraw app seems to do it periodically. I've added 
notifyoff("sys: window size change") to my copy of page.c, which has 
solved the problem here. Exactly why other apps, which don't explicitely 
handle it are only sometimes affected, or why I've only noticed the 
problem with libdraw apps, and only since the introduction of devdraw, I 
can't say.