I actually noted this in the unofficial tarball you rolled for me in December:
I'm not sure why one is trying to build the usnic btl on Solaris at all.
Perhaps just because the OFED stack is present?
I assumed your lack of response meant Cicso had some plans for Solaris support that you could "neither confirm nor deny" ;)
Attached are the configure outputs and config.log from both the trunk and 1.7-latest on a 64-bit Solaris-11 system.
I can provide 32-bit if required, but the usnic BTL is built independent of wordsize:
$ bzgrep 'usnic can compile' openmpi-*.bz2
openmpi-1.7-latest-solaris11-x64-ib-gcc452-configure.txt.bz2:checking if MCA component btl:usnic can compile... yes
openmpi-trunk-solaris11-x64-ib-gcc452-configure.txt.bz2:checking if MCA component btl:usnic can compile... yes