Outdated typedefs in documentation

Hi,
I have noticed a slight mismatch between typedefs in docs and header
files. On current master branch:
- CustomScanState is missing custom_ps, pscan_len and slotOps fields
in docs.
- `methods` field of CustomPath, CustomScan and CustomScanState is
missing `struct` in type.
- BrinOpcInfo.oi_regular_nulls is missing.
- pgNotify.next is missing. But the comment above it says apps should
not use it, so I guess it can be left as is.

Attached diff file shows other mismatches I could find. There are some
comments that could be updated. Other differences are caused by
indentation variations and false positives. The script I used for
typedef extraction is also attached.

Regards,
Artem Fadeev.
https://postgrespro.com