mingw32-curl: Upgrade to 7.38.0

The patch is already included upstream.

Signed-off-by: Thomas Braun <thomas.braun@byte-physics.de>
Prefer generic mgwport commands

Signed-off-by: Thomas Braun <thomas.braun@byte-physics.de>
Merge pull request #24 from t-b/upgrade_curl

Upgrade curl to 7.38.0