MFC r252895: Add a man page for the SDT_* macros
MFC r253720: Use kern_ioctl() rather than ioctl() for testing the FBT provider
MFC r254468,r254469: Add a "translated type" argument to SDT_PROBE_ARGTYPE()

Note: this breaks ABI compatibility with older modules with SDT probes.

My opinion is that benefits outweigh downsides, because I am not aware
of any thirdparty binary-only modules with SDT probes.