Always write mapsize = max(other metapage:mapsize, env:mapsize).

Revert "ITS#7789 Fix resize vs MDB_NOMETASYNC, and a comment."
Revert "ITS#7789 more"
Revert "Revert "ITS#7789 update RESIZED errmsg text""
Revert "ITS#7789 update RESIZED errmsg text"
Revert "ITS#7789 persist mapsize changes"

This reverts commit 02285aca.
This reverts commit 38e71c68.
This reverts commit a5e4eecb.
This reverts commit d8e18551.
This reverts commit 5926e54b.

Don't pass non-NULL map address unless MDB_FIXEDMAP was used.

Must also set in sub-cursor if deleting entire subDB

Always set the filesize when opening for writes. Otherwise
can't use backups from mdb_copy.

We mainly use Win32 functions, so cannot just use C-runtime strerror
to return error messages. We have to use Win32-specific messages.
Unfortunately, we document the API to return C-runtime error codes,
so we can't just switch to all Win32 error codes.

Off-by-one in end check, would complain on valid input.

persist size changes from env_open() as well. This was the
original behavior.

This reverts commit d8e18551.
And partially reverts mapsize check. Only mapsize increases are relevant.

Set read txn's dbiseqs to env's. Set child txn's dbiseqs to parent's.
Simplify DBI_CHANGED test, no need to check md_name. No-op dbi_close
of already closed handle.

only update dbiseq in dbi_open on write txns

dbiseqs are only checked in write txns so omit from read txns

Use DBI sequence numbers to detect DBIs being closed while in use.

Write decreases too, not just increases. Check for any size change
that was not requested by this process.

'#ifdef MDB_DEVEL' -> '#if MDB_DEVEL'
Fix comments, use actual PAGEBASE macro as originally intended.
Actually enable 64K pages. Set MDB_DATA_VERSION for testing only.

mdb_txn_commit(child): Give loose pages to parent.
Use a pointer beyond the page header instead of mp_next, so
we will not need to save/restore mp_pgno. This avoids a crash
caused by references to mp_pgno.

Fix in 534dcc72 was in wrong place

Fix mp_lower/mp_upper to exclude PAGEHDRSZ, which means our
max mp_upper is now pagesize - PAGEHDRSZ and won't overflow.
Currently must define MDB_DEVEL to use. Will be default for
LMDB 1.0/OpenLDAP 2.5

Use gcc section attribute to keep less frequently used functions
away from main code.

Make sure the writer thread starts and stops when we expect it to.