MFH: r420174

multimedia/libmtp: update to 1.1.12

Changes: https://sourceforge.net/projects/libmtp/files/libmtp/1.1.12/README/view
ABI: https://people.freebsd.org/~jbeich/compat_reports/libmtp/1.1.11_to_1.1.12/compat_report.html
Approved by: ports-secteam (junovitch)