docs: Add a section on version checking macros
This is a port to GLib of changes originally made in the GTK copy of these docs, at gtk@72b0a443.
(Copied across by Philip Withnall.)
Helps: #3037 (closed)
This is a port to GLib of changes originally made in the GTK copy of these docs, at gtk@72b0a443.
(Copied across by Philip Withnall.)
Helps: #3037 (closed)