Fix mv8plus, allow targetting Linux or Solaris from other sparc host.

Fix mv8plus, allow targetting Linux or Solaris from other sparc host.

	* config/sparc/sol2.h: Protect -m{cpu,tune}=native handling
	with a more complete cpp test.
	* config/sparc/linux64.h: Likewise.
	* config/sparc/linux.h: Likewise.
	* config/sparc/sparc.opt (sparc_debug): New target variable.
	(mdebug): New target option.
	* config/sparc/sparc.h (MASK_DEBUG_OPTIONS, MASK_DEBUG_ALL,
	TARGET_DEBUG_OPTIONS): New defines.
	* config/sparc/sparc.c (debug_target_flag_bits,
	debug_target_flags): New functions.
	(sparc_option_override): Add name strings back to cpu_table[].
	Parse -mdebug string.  When TARGET_DEBUG_OPTIONS is true, print
	out the target flags before and after override processing as well
	as the selected cpu.  If MASK_V8PLUS, make sure that the selected
	cpu is at least v9.

From-SVN: r180021