Default to /mingw/bin/curl-ca-bundle.crt for https certificates

The curl executable uses that file as a source for root certificates,
but running curl as a library does not do that automatically.  So we
have to tell Git about that file.

Suggested by Bosko Ivanisevic.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

etc/gitconfig

@@ -7,3 +7,5 @@
 	packSizeLimit = 2g
 [help]
 	format = html
+[http]
+	sslCAinfo = /mingw/bin/curl-ca-bundle.crt