[Sync-EN] Document the odbc fetch row default value change to null

[lacatoire]

Syncs the three reference/uodbc/functions/odbc-fetch-* pages with php/doc-en#5768.

• The row parameter is described properly on all three pages: it is a 1-based row number, omitting it or passing null fetches the next row as odbc_fetch_row() does, and drivers that cannot fetch by number ignore it. Previously it said only "the row number" or "optionally choose which row number to retrieve".
• The 8.4.0 changelog rows now also state the default value change, from -1 (odbc_fetch_array(), odbc_fetch_object()) or 0 (odbc_fetch_into()) to null, consistent with odbc_fetch_row().

EN-Revision bumped to 5035039fb951eac2330431bf47dc4a50e1ef9ee9 on the three files.

Fixes: #1632