dirmngr: More binary I/O on Windows for CRLs

* dirmngr/crlcache.c (lock_db_file, crl_cache_insert): Open cache
file in binary mode.

CRLs on Windows would have line ending entries converted. This
did not cause problems in a surprising amount of cases but
can lead to unexpected and random parse / read errors. Especially
with large CRLs like cacert.

This bug has been around since 2004.

• GnuPG-Bug-Id: T3923
• Signed-off-by: Andre Heinecke <aheinecke@intevation.de>