app-emulation/qemu: version bump to 3.1.0

app-emulation/qemu: version bump to 3.1.0

 - use RESTRICT=strip, bug #651422

 - switch to tar.xz, bug #666726

 - add missing use constraints, bug #664474

   qemu_softmmu_targets_riscv32? ( fdt )
   qemu_softmmu_targets_riscv64? ( fdt )

 - 3.1.0 already contains patches for CVE-2018-15746

 - applied patch for CVE-2018-20123

 - disable bt subsystem entirely as a "workaround" for CVE-2018-19665.

   Upstream deprecated the subsystem in November and states that it had
   been dysfunctional for years with likely no users.

Bug: https://bugs.gentoo.org/664740
Bug: https://bugs.gentoo.org/672346
Bug: https://bugs.gentoo.org/673108
Closes: https://bugs.gentoo.org/651422
Closes: https://bugs.gentoo.org/664474
Closes: https://bugs.gentoo.org/666726
Package-Manager: Portage-2.3.52, Repoman-2.3.12
Signed-off-by: Matthias Maier <tamiko@gentoo.org>