The result of rounding a 128-bit BFP/DFP value to 32/64 bit needs to
be stored in a register pair. This constraint was not observed previously
and the result was stored in any FPR that happened to be chosen. If the
selected FPR was not identifying a proper FPR pair, a SIGILL was delivered.
Fixes BZ #328455.


git-svn-id: svn://svn.valgrind.org/vex/trunk@2801 8f6e269a-dfd6-0310-a8e1-e2731360e62c