Handle memory error in print_insn_rx

Handle memory error in print_insn_rx

Nowadays, memory error in rx disassembly is not handled, so if I
start a fresh GDB, and disassemble,

(gdb) set architecture rx
The target architecture is assumed to be rx
(gdb) disassemble 0x0,+4
Dump of assembler code from 0x0 to 0x4:
   0x00000000:	brk
   0x00000001:	brk
   0x00000002:	brk
   0x00000003:	brk

the output is wrong.  This patch adds code to call dis->memory_error_func
on memory error, and longjmp to print_insn_rx.  With this patch applied,

(gdb) set architecture rx
The target architecture is assumed to be rx
(gdb) disassemble 0,+4
Dump of assembler code from 0x0 to 0x4:
   0x00000000:	Cannot access memory at address 0x0

opcodes:

2016-12-12  Yao Qi  <yao.qi@linaro.org>

	* rx-dis.c: Include <setjmp.h>
	(struct private): New.
	(rx_get_byte): Check return value of read_memory_func, and
	call memory_error_func and OPCODES_SIGLONGJMP on error.
	(print_insn_rx): Call OPCODES_SIGSETJMP.