if_tap: Handle 'SIOCSIFMTU' ioctl directly to support MTU > 1500
Add the SIOCSIFMTU ioctl handling directly to tap(4) permitting it to
have its MTU set higher than 1500 (ETHERMTU). Its new limit is now
65535 as enforced by 'ifhwioctl()' in 'if.c'.
This allows a tap(4) device to be added to a bridge, which requires all
interface members to have the same MTU, with an interface configured for
jumbo frames. QEMU may now connect to a network via tap(4) without
requiring the real interface to have its MTU set to 1500 or lower.
Also bump __DragonFly_version.
Obtained-from: FreeBSD (revision 189866)
UnifiedSplitRaw
