compilers.conf.5: Remove docs about *_VERSION, it no longer exists.
mxge(4): Fix "always_inline function might not be inlinable" warning.

The '__attribute__((always_inline))' does not strictly imply 'inline'.
Newer versions of gcc detect this misuse and issue the warning.
Including the missing 'inline' resolves the build warning.
make device_probe_child() public
HAMMER VFS - Use full-block undos for B-Tree nodes

* Use a full-block undos instead of small byte-range undos for
  B-Tree nodes.

  There is no bug here per-say, but we are trying to improve
  HAMMER's ability to recover after a power failure where a disk
  drive is writing to the platter at the time of the failure.
  While we have no control over any unrelated sectors that might
  get smashed by such an event, the concern is that sectors being
  specifically written might get corrupted beyond the ability for
  the byte-range undo to fix.

  The reason is that if, say, only 50 bytes in a B-Tree node need
  updating, HAMMER must still do a 16K physical write to disk, so
  really any portion of that 16K can wind up corrupt on a power
  failure, not just the 50 bytes being changed.

  So instead of writing a byte-ranged 50-byte UNDO we now write
  a 16K undo for B-Tree elements.

* The hope is that this will improve cases where HAMMER has become
  unmountable due to CRC errors in the B-Tree closer to the root of
  the B-Tree (which are usually updated to update only the mirror_tid)

Reported-by: sgeorge, marino
kernel - Fix sysclock_t comparison in usched code

* Fix a sysclock_t comparison that was attempting to detect an overflow
  by checking if an unsigned field was negative.  The field has
  to be cast to signed for the test to work as expected.

Reported-by: enjolras
kernel - set machdep.pmap_mmu_optimize to 1 by default in master

* Set machdep.pmap_mmu_optimize to 1 by default in master.

* Note that the sysctl will be left defaulted to 0 in the 3.2 release
  because it is too new a feature.  However, we believe it to be stable.
vkernel - Adjust parameters for vkernel test build

* Increase root partition from 512M to 2G to accomodate DEBUG_FLAGS=-g
  kernels.

* Increase default memory from 128M to 256M

* Create the /var/vkernel directory if necessary.
compilers.conf.5: Some more cleanup.

* Remove a reference to an old patch I did for building world with clang.
  The changes which are currently needed remain to be determined.

* Make the examples more generic and indicate that buildworld/kernel
  do not necessarily survive with the compilers listed. Also, stuff them
  into an EXAMPLES section.

* Add a comma.

Reported-by: Carsten Mattner <carstenmattner@gmail.com>
Bring in USB4BSD userspace libraries and utilities.

The following will now be built and installed if WANT_USB4BSD is defined.

* libusb
* usbconfig
usb4bsd: Pull up libusb and usbcontrol to FreeBSD current's.

I stopped before their recent streams commit.
make upgrade: Remove more new USB stuff if it is not requested.

To reduce confusion when switching.
kernel: add device_delete_children()

Obtained-from: FreeBSD
usb4bsd/controller: Use device_delete_children().
emx: Group TX related fields into emx_txdata; use it in TX related functions
emx: Cache align software TX/RX descriptors
Merge branch 'master' into gsocdrm_alter