Proposed Update UAX #31, Unicode Identifier and Pattern Syntax

Unicode Standard Annex #31, Unicode Identifier and Pattern Syntax, will be updated for Unicode 9.0. The proposed update is now available for general public review and comment.

A major change in the proposed update is the addition of a new section with recommended syntax for Unicode hashtags, also including emoji characters.

The draft also makes it clearer that XID_Start/Continue properties are preferred over ID_Start/Continue, and modifies the syntax of the definition to customization cleaner, and allow for medial-only characters in identifiers.