[DWARF] Enable DW_CFA_VAL_EXPRESSION support

[DWARF] Enable DW_CFA_VAL_EXPRESSION support

gcc/
	* reg-notes.def (CFA_VAL_EXPRESSION): New entry.
	* dwarf2cfi.c (dwarf2out_frame_debug_cfa_val_expression): New function.
	(dwarf2out_frame_debug): Support REG_CFA_VAL_EXPRESSION.
	(output_cfa_loc): Support DW_CFA_val_expression.
	(output_cfa_loc_raw): Likewise.
	(output_cfi): Likewise.
	(output_cfi_directive): Likewise.
	* dwarf2out.c (dw_cfi_oprnd1_desc): Support DW_CFA_val_expression.
	(dw_cfi_oprnd2_desc): Likewise.
	(mem_loc_descriptor): Recognize new pattern generated for value
	expression.

From-SVN: r241826