Add support for ANSI SGR escape code 3 (italics)

Adds support for escape sequences \e[3m and \e[23m (to turn italics on
and off respectively).
http://en.wikipedia.org/wiki/ANSI_escape_code#CSI_codes

Patch by Jem Orgun jeorgun@gmail.com
FEATURE: 314410
REVIEW: 108844
FIXED-IN: 4.11