doc: Add since version tag to libusb_set_log_cb() The commit f74c7f5 "core: new API libusb_set_log_cb() to redirect global and per context log messages to the provided log handling function" in 2018-12-05 is present from 1.0.23 onwards. This commit just adds this to the docs. Closes #872 Signed-off-by: Victor Toso <victortoso@redhat.com> Signed-off-by: Chris Dickens <christopher.a.dickens@gmail.com>