common,w32: Add missing GetLastError->errno mapping.
* common/iobuf.c (file_filter, sock_filter): Add missing mapping.
(cherry picked from commit 5e94470d053ec93f79acb03635e67839a5a1e6a8)
Also includes commit a3be97df4ddfce008dcc6e877e9fb98c71656ec6
- GnuPG-bug-id: T6528