737931 - Add support for Unicode Script_Extensions property

Status: NEW

Description

[Simon Montagu :smontagu]

Unicode 6.1 added a new Script_Extensions property, defined for a number of code points in the data file http://unicode.org/Public/6.1.0/ucd/ScriptExtensions.txt 

# The Script_Extensions property indicates which characters are commonly used
# with a limited number of scripts, but with more than one.
# The property is provisional: values are expected to change over time as more information becomes available.
# For each code point, there is one or more property values.  Each such value is a Script property value.
# For more information, see:
#   UAX #24: http://www.unicode.org/reports/tr24/ and
#   UAX #44: http://www.unicode.org/reports/tr44/

We want to use this property for more accurately identifying mixed-script hostnames in bug 722299 (or a follow-up to that bug). I don't know if font code would also want to use it.