Merge branch 'tb/xcurl-off-t'

The xcurl_off_t() helper function is used to cast size_t to curl_off_t, but some compilers gave warnings against the code to ensure the casting is done without wraparound, when size_t is narrower than curl_off_t. This warning has been squelched. * tb/xcurl-off-t: remote-curl.c: xcurl_off_t is not portable (on 32 bit platfoms)