(jump_optimize): In no-nop move deletion, don't test
PRESERVE_DEATH_INFO_REGNO_P; instead test if optimization is performed.
Check for REG_UNUSED note on to-be deleted insn before searching for preceding
instruction to delete note from.
If PRESERVE_DEATH_INFO_REGNO_P is true for SREG, replace INSN with USE.

From-SVN: r12783