HS 2.0: Allow printf format parsing with language:name strings

HS 2.0: Allow printf format parsing with language:name strings

This allows Hotspot 2.0 and Interworking strings that use language:name
string (e.g., venue_name) to be encoded using printf format to enter
special characters like newline.

Signed-hostap: Jouni Malinen <jouni@qca.qualcomm.com>