(bug 4907) Enable redirection for ios homescreen icons in S2

Added configuration instructions in doc/config-local.pl.txt
with commented-out version which works with current dw install.
Header linkref for ios homescreen icon is added if config
variable is present in any page served through S2.
Merge pull request #465 from dwmc15873/bug4907-ios-icon

(bug 4907) Teach S2 to serve up icons for iOS