[Vala] gtk+-3.0 bindings - big change little end user impact (hopefully)

[Al Thomas <astavale yahoo co uk>]

Hello Fellow Vala Fans,
A long standing change to generate the GTK+ 3 bindings from GIR, instead of usingthe older GIDL method, has 
now gone into Vala mainline:
https://git.gnome.org/browse/vala/commit/?id=a8e6aff63e5e1502290ba93398314acf2ad45b60
This enables better bindings to be generated more easily and has already resolved 
twobugs:https://bugzilla.gnome.org/show_bug.cgi?id=791130https://bugzilla.gnome.org/show_bug.cgi?id=791570
Thanks to Evan Nemerson and Rico Tzschichholz for starting and finishing this work, respectively.

The newly generated bindings are now available for testing in the 0.39.2 preview release and will be 
available from Vala 0.40. The changes should have minimal impact. They have already passed building many Vala 
projects that are in Vala CI. See this build:http://paldo.org:8010/builders/vala-staging/builds/356
If a binding has changed, for example a parameter has become nullable, you may needto use conditional 
pre-parsing in your Vala code:#if VALA_0_40    // New binding call#else    // Old binding call#endif

If you believe there is an error in a binding please raise a ticket through our bugzilla.
The 0.39.2 preview release has already had some external testing. A regression was found andbug report with 
test case raised. The issue was a side effect of work to reduce the numberof temporary variables used in Vala 
generated C and has now been fixed. If you are usinginheritance to chain up setting a struct at instantiation 
time then details are here:https://bugzilla.gnome.org/show_bug.cgi?id=791785
All the best,
Al