This is the new implementation of how to make platform-safe native keys,
for which no past compatibility is required nor promised. Unlike when we
started in Qt 4.4, it doesn't look there are many restrictions in names
anyway.
Important differences are:
* POSIX RT: no restrictions, we prepend the necessary '/'
* System V/XSI: no restrictions, it's just a file path anyway;
we pass absolute paths unchanged; otherwise we prepend RuntimeLocation
* Windows: no restrictions, but we do recognize Global\ and Local\
kernel objects without munging them
The use of the RuntimeLocation may cause a warning on Unix systems
(other than Apple ones and Android) if $XDG_RUNTIME_DIR isn't set.
We do enforce the Apple 30-character limit here, otherwise you get
ENAMETOOLONG.
Change-Id: I12a088d1ae424825abd3fffd171d3a0e09e06361
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
0b79f58458