re PR c/13801 (Decls should regain old type at end of scope)

	PR c/13801
	* c-decl.c (struct c_binding): Add type and inner_comp fields.
	(bind): Set type and inner_comp fields.
	(pop_scope): Restore type of decl to the correct type from an
	outer scope.  Give error when popping file scope for incomplete
	arrays completed incompatibly with default initialization in an
	inner scope.
	(diagnose_mismatched_decls): Handle externs with initializers at
	block scope.
	(pushdecl): Set type of external declaration at block scope based
	only on the visible declarations.  Save type when changing the
	type of a declaration.  Merge an external declaration at block
	scope with a visible static declaration at file scope.
	(implicitly_declare): Give recycled old declaration the new type
	except for incompatible declarations of built-in functions, saving
	the old type.

testsuite:
	* gcc.dg/redecl-3.c, gcc.dg/redecl-4.c, gcc.dg/redecl-6.c,
	gcc.dg/redecl-7.c, gcc.dg/redecl-8.c, gcc.dg/redecl-9.c,
	gcc.dg/redecl-10.c, gcc.dg/debug/redecl-1.c,
	gcc.dg/debug/redecl-2.c, gcc.dg/debug/redecl-3.c,
	gcc.dg/debug/redecl-4.c, gcc.dg/debug/redecl-5.c: New tests.

From-SVN: r86636