i386[stv]: Handle REG_EH_REGION note

When we split
(insn 37 36 38 10 (set (reg:DI 104 [ _18 ])
        (mem:DI (reg/f:SI 98 [ CallNative_nclosure.0_1 ]) [6 MEM[(struct SQRefCounted *)CallNative_nclosure.0_1]._uiRef+0 S8 A32])) "test.C":22:42 84 {*movdi_internal}
     (expr_list:REG_EH_REGION (const_int -11 [0xfffffffffffffff5])

into

(insn 104 36 37 10 (set (subreg:V2DI (reg:DI 124) 0)
        (vec_concat:V2DI (mem:DI (reg/f:SI 98 [ CallNative_nclosure.0_1 ]) [6 MEM[(struct SQRefCounted *)CallNative_nclosure.0_1]._uiRef+0 S8 A32])
            (const_int 0 [0]))) "test.C":22:42 -1
        (nil)))
(insn 37 104 105 10 (set (subreg:V2DI (reg:DI 104 [ _18 ]) 0)
        (subreg:V2DI (reg:DI 124) 0)) "test.C":22:42 2024 {movv2di_internal}
     (expr_list:REG_EH_REGION (const_int -11 [0xfffffffffffffff5])
        (nil)))

we must copy the REG_EH_REGION note to the first insn and split the block
after the newly added insn.  The REG_EH_REGION on the second insn will be
removed later since it no longer traps.

gcc/ChangeLog:

	* config/i386/i386-features.cc
	(general_scalar_chain::convert_op): Handle REG_EH_REGION note.
	(convert_scalars_to_vector): Ditto.
	* config/i386/i386-features.h (class scalar_chain): New
	memeber control_flow_insns.

gcc/testsuite/ChangeLog:

	* g++.target/i386/pr111822.C: New test.