Fix problems due to generating Neon instructions on non-Neon capable
hosts:
* iselNeon64Expr, iselNeonExpr: assert that the host is actually
Neon-capable.
* iselIntExpr_R_wrk, existing cases for Iop_GetElem8x8,
Iop_GetElem16x4, Iop_GetElem32x2, Iop_GetElem8x16, Iop_GetElem16x8,
Iop_GetElem32x4:
Limit these to cases where the host is Neon capable, else we wind up
generating code which can't run on the host.
* iselIntExpr_R_wrk: add alternative implementation for
Iop_GetElem32x2 for non-Neon capable hosts.
git-svn-id: svn://svn.valgrind.org/vex/trunk@3098