A macro to mark tech preview APIs, in order to make header reviews
easier:
* newly introduced TP APIs are clearly marked as such;
* an API that leaves TP and becomes stable requires to change the
header, and not just the documentation (and therefore will again
appear in the header review).
The idea is to use this macro as if it were a C++ attribute.
It can't actually be an attribute, because we want to use it to tag
e.g. macro expansions (like Q_PROPERTY).
Change-Id: I05c5a91a4fa5bedfbd1c6146d4dc00e1d1d28628
Pick-to: 6.7
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
32a1151245