re PR c/10178 (ICE in tree_low_cst)

	PR 10178
	* langhooks.h (struct lang_hooks): Add no_body_blocks bool.
	* langhooks-def.h (LANG_HOOKS_NO_BODY_BLOCKS): New; default false.
	* c-lang.c, objc/objc-lang.c: Override LANG_HOOKS_NO_BODY_BLOCKS
	to true.
	* stmt.c (is_body_block): If lang_hooks.no_body_blocks, always
	return 0.

From-SVN: r68483