MIPS16/GAS: Disallow EXTEND delay-slot scheduling

MIPS16/GAS: Disallow EXTEND delay-slot scheduling

Do not allow any explicitly coded EXTEND instruction to be automatically
scheduled into a jump delay slot, as an EXTEND prefix is coupled with
the next regular MIPS16 instruction and therefore swapping it with a
jump would change program's semantics; EXTEND is not architecturally
allowed to be present in a jump delay slot anyway.

	opcodes/
	* mips16-opc.c (mips16_opcodes): Set NODS in `pinfo' for
	"extend".

	gas/
	* testsuite/gas/mips/mips16-extend-swap.d: New test.
	* testsuite/gas/mips/mips16-extend-swap.s: New test source.
	* testsuite/gas/mips/mips.exp: Run the new test.