arm32: support (ARM) PLDW [reg, #imm].  The non-W variant was already
accepted.  Fixes #323179.  (vasily.golubev@gmail.com)



git-svn-id: svn://svn.valgrind.org/vex/trunk@2896 8f6e269a-dfd6-0310-a8e1-e2731360e62c