Boehm GC import

[Tom Tromey]

FYI: I've imported version 4.14 of the Boehm GC into libgcj/boehm-gc
on the vendor branch.  I have not yet merged it with the trunk, and
don't plan to do so in the near future.  I did this import in case
anybody (Alexandre :-) wants to extract patches for new ports in 4.14
for possible inclusion in the 2.95 branch.

I'll do the full merge "sometime", probably after 2.95 is released.

Tom