* gnu/packages/patches/gtk-doc-respect-xml-catalog.patch: New file.
* gnu/local.mk (DIST_PATCH_DATA): Add it.
* gnu/packages/gtk.scm (gtk-doc): Update to 1.33.2.
[source]: Add gtk-doc-respect-xml-catalog.patch patch.
[build-system]: Switch to meson.
[arguments]: Remove fix-docbook phase.
Remove configure flags that are no longer needed.
[outputs]: Remove the help output since the help-dir option no longer exists.
