GLib C type conventions

• Prefer standard C types over GLib aliases that add no meaning. For example, use char, size_t, uint8_t, uint32_t, and int64_t instead of gchar, gsize, guint8, guint32, and gint64 in new code.
• Use size_t for array indexes, collection lengths, and loop counters compared with a size or length.
• Preserve gsize when it is already established in older surrounding code; do not introduce it for new index or length variables.
• Use a GLib type when it carries useful semantics or is needed to match an existing public API, callback signature, or surrounding interface. Do not replace types mechanically when that would alter signedness, width, or compatibility.