[NDS32] Implement more C ISR extension.

[NDS32] Implement more C ISR extension.

gcc/
	* config.gcc (nds32*): Add nds32_isr.h and nds32_init.inc in
	extra_headers.
	* common/config/nds32/nds32-common.c (nds32_handle_option): Handle
	OPT_misr_secure_ case.
	* config/nds32/nds32-isr.c: Implementation of backward compatibility.
	* config/nds32/nds32-protos.h (nds32_isr_function_critical_p): New.
	* config/nds32/nds32.c (nds32_attribute_table): Add critical and
	secure attribute.
	* config/nds32/nds32.h (nds32_isr_nested_type): Add NDS32_CRITICAL.
	(nds32_isr_info): New field security_level.
	(TARGET_ISR_VECTOR_SIZE_4_BYTE): New macro.
	* config/nds32/nds32.md (return_internal): Consider critical attribute.
	* config/nds32/nds32.opt (misr-secure): New option.
	* config/nds32/nds32_init.inc: New file.
	* config/nds32/nds32_isr.h: New file.

libgcc/
	* config/nds32/t-nds32-isr: Rearrange object dependency.
	* config/nds32/initfini.c: Add dwarf2 unwinding support.
	* config/nds32/isr-library/adj_intr_lvl.inc: Consider new extensions
	and registers usage.
	* config/nds32/isr-library/excp_isr.S: Ditto.
	* config/nds32/isr-library/intr_isr.S: Ditto.
	* config/nds32/isr-library/reset.S: Ditto.
	* config/nds32/isr-library/restore_all.inc: Ditto.
	* config/nds32/isr-library/restore_mac_regs.inc: Ditto.
	* config/nds32/isr-library/restore_partial.inc: Ditto.
	* config/nds32/isr-library/restore_usr_regs.inc: Ditto.
	* config/nds32/isr-library/save_all.inc: Ditto.
	* config/nds32/isr-library/save_mac_regs.inc: Ditto.
	* config/nds32/isr-library/save_partial.inc: Ditto.
	* config/nds32/isr-library/save_usr_regs.inc: Ditto.
	* config/nds32/isr-library/vec_vid*.S: Consider 4-byte vector size.

From-SVN: r263493