VLD4/VST4: generate in-line interleave/de-interleave code, so that
loads can always be done in 8 byte units.


git-svn-id: svn://svn.valgrind.org/vex/trunk@2711 8f6e269a-dfd6-0310-a8e1-e2731360e62c
Generate better code for Shl64(x, imm8) since the Neon front end
produces a lot of those for V{LD,ST}{1,2,3,4}.


git-svn-id: svn://svn.valgrind.org/vex/trunk@2712 8f6e269a-dfd6-0310-a8e1-e2731360e62c