[vala] (5 commits) Non-fast-forward update to branch wip/issue/767

[Rico Tzschichholz <ricotz src gnome org>]

The branch 'wip/issue/767' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  95522f7... codegen: Implement silent-cast for basic typed variants
  675778a... WIP Extend silent-cast support to type with known type sign

Commits added to the branch:

  0ed8cad... codegen: Don't create special GArray clear-func for non-nul (*)
  906f76d... codegen: Resolve generics in sizeof-expression of parameter (*)
  f83ecd8... codegen: Use default-value to pass element_size to GArray c (*)
  1fa4a17... tests: Add "struct (un)boxing" variant test
  69d448d... WIP codegen: Implement silent-cast for GLib.Variant

(*) This commit already existed in another branch; no separate mail sent