[gdk-pixbuf] (6 commits) Non-fast-forward update to branch doc-fixes

[Emmanuele Bassi <ebassi src gnome org>]

The branch 'doc-fixes' 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:

  317bea9... docs: Move the core data section to the source file
  7abf491... Add `gtk_doc` build option
  461530a... ci: Build and deploy the API reference

Commits added to the branch:

  3756f7b... io-bmp.c: Fix building on older compilers (*)
  7ebedf3... XBM: Fix signed integer overflow. (*)
  c22494b... XPM: Fix undefined behaviour (*)
  1479726... docs: Move the core data section to the source file
  716158e... Add `gtk_doc` build option
  c7eada6... ci: Build and deploy the API reference

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