c-tree.h: Delete COMPARE_DIFFERENT_TU from enumeration.

	* c-tree.h: Delete COMPARE_DIFFERENT_TU from enumeration.
	* c-typeck.c (same_translation_unit_p): New function.
	(comptypes): Use it instead of flags parameter to identify
	structure types from different translation units.
	* c-decl.c (duplicate_decls): Always call comptypes with
	COMPTYPE_STRICT flags argument.
	(c_reset_state): Set BLOCK_SUPERCONTEXT of the block formed
	to file_scope_decl.

From-SVN: r70953