1. in libcmis, pass the CurlInitProtocolsFunction to all subclasses of
   HttpSession that need it, and add 2 upstream fixes to pass it around

2. Arrange for InitCurl_easy to be called in UCP RepoContent as well

3. If AllowInsecureProtocols is disabled, automatically upgrade
   http connections to https, as is already done in webdav-curl.
   Do this in Content and RepoContent; hopefully should work
   to convert when m_aURL member is initialised;
   the m_xIdentifier on the other hand should have the original
   URL because ContentProviderImplHelper::queryExistingContents()
   caching likely relies on that.

Change-Id: I20d36ed03ba7ce221d6946b1c996071f4130ec7e
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/169114
Tested-by: Jenkins
Reviewed-by: Michael Stahl <michael.stahl@allotropia.de>