FreeBSD ARM EABI in head

[Andrew Turner]

I have finished merging in my changes from the ARM EABI project branch
into head. I would appreciate it if people would be able to test it.

To build it you will need a checkout of head no earlier than r245942.
You can then run the normal build procedure with WITH_ARM_EABI set, for
example:
make TARGET_ARCH=armv6 -DWITH_ARM_EABI buildworld
make TARGET_ARCH=armv6 -DWITH_ARM_EABI buildkernel TARGET=RPI-B

If your kernel config includes DDB you will need to set WITH_ARM_EABI
when building your kernel to get backtrace support.

I have tested the ARM EABI branch on arm and armv6 and the head merge on
armv6 and expect these two to mostly work. As I have no access to any
big-endian ARM hardware I have been unable to test there.

There are currently three known issues:
* No clang support - this should be fixed soon, I'm waiting on another
  patch to go into head first.
* No gdb - I'm testing a fix for this.
* No bind utils - for some reason the bind tools, e.g. dig, segfault in
  the sig_wait syscall.

Andrew