Add 32-bit compat support for AIO.
Add 32-bit compat support for AIO.

jhb probably forgot to commit this file with r185878 and will want to
review this. It unbreaks the build here.

Obtained from:	p4 //depot/user/jhb/lock/compat/freebsd32/freebsd32_signal.h#2

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase