`PRODID` is folded when it has exactly 75 characters

[rfc2822]

When PRODID has exactly 75 characters, it's folded without obvious reason:

VCALENDAR
VERSION:2.0
PRODID:DAVx5/4.5.5-gplay ical4j/3.2.19 (com.simplemobiletools.calendar.pro)
 
BEGIN:VEVENT

This can happen for special combinations of DAVx5 version numbers and calendar app package names.

Although it may be technically valid, it's confusing and there are servers like iCloud which seem to reject such iCalendars.

[rfc2822]

• Added test in PR: Add test for PRODID folding #142
• Created upstream issue: Properties are folded when line is exactly max line length ical4j/ical4j#832