man: Add feature macro WAFFLE_API_EXPERIMENTAL
man: Add feature macro WAFFLE_API_EXPERIMENTAL

waffle_window_resize() is proving difficult to implement because Waffle
lacks an event model.  We need a way to prevent clients from
accidentally using it, on the master branch as well in stable releases,
until it gets fixed or removed.

All future API additions that I have strong doubts about will get
guarded by WAFFLE_API_EXPERIMENTAL.

Signed-off-by: Chad Versace <a557f7f75bf28dc19ac99107f5cc7cd6b3fbdb1a@linux.intel.com>

yinquan529/waffle-gl-waffle,yinquan529/waffle-gl-waffle,janesma/waffle,waffle-gl/waffle,dcbaker/waffle,evelikov/waffle,waffle-gl/waffle,fjhenigman/waffle,maurossi/waffle,maurossi/waffle,evelikov/waffle,fjhenigman/waffle,chadversary/waffle,maurossi/waffle,janesma/waffle,janesma/waffle,fjhenigman/waffle,dcbaker/waffle,chadversary/waffle,waffle-gl/waffle,evelikov/waffle,chadversary/waffle,waffle-gl/waffle,yinquan529/waffle-gl-waffle,dcbaker/waffle