arm.c (bad_signed_byte_operand): New predicate function.

* arm.c (bad_signed_byte_operand): New predicate function.
* arm.h (PREDICATE_CODES): Add it to the list.
* arm.md (*extendqi[sh]i_insn): Split any addresses that ldrsb
can't handle.
(define_split): Two new splits for above insns.

From-SVN: r20057