3cc092ff06
now used for printing diagnostic messages through the kernel message buffer. this lets processes print diagnostics without sending messages to tty and log directly, simplifying the message protocol a lot and reducing difficulties with deadlocks and other situations in which diagnostics are blackholed (e.g. grants don't work). this makes DIAGNOSTICS(_S), ASYN_DIAGNOSTICS and DIAG_REPL obsolete, although tty and log still accept the codes for 'old' binaries. This also simplifies diagnostics in several servers and drivers - only tty needs its own kputc() now. . simplifications in vfs, and some effort to get the vnode references right (consistent) even during shutdown. m_mounted_on is now NULL for root filesystems (!) (the original and new root), a less awkward special case than 'm_mounted_on == m_root_node'. root now has exactly one reference, to root, if no files are open, just like all other filesystems. m_driver_e is unused.