The commit "Fix fcntl64 for 64 bit targets" (http://git.buildroot.net/uClibc/commit/?id=6f1daaaf2d94c1e6184add44eda38b0781b88cf0) is fixing a bug that exists in 0.9.31, so it should probably be applied as well in the 0.9.31 branch, so as to be part of the next bug-fix release of this branch.
I've scheduled that for 0.9.31.2 now. Thanks for the heads up!