More called details fixup for skinny.

Basically sets the callerid and callername to the first device talked to for the
purposes of putting the the calls made log on the device. Does not affect the device
displaying who the device is currently talking to.

Also some minor changes to use sub->exten in lieu of l->lastnumberdialed.

(closes issue ASTERISK-21095)
Reported by: wedhorn
Tested by: snuffy, myself
Patches: 
    skinny-calllogsoutbound03.diff uploaded by wedhorn (license 5019)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@382008 65c4cc65-6c06-0410-ace0-fbb531ad65f3