* c-decl.c (grokdeclarator): In C99 mode, give the more specific
	"return type defaults" warning for functions with return type
	defaulting to int.
	* c-lang.c (c_init): In C99 mode, enable warnings for implicit
	function declarations by default rather than only when pedantic.

testsuite:
	* gcc.dg/c99-impl-int-1.c: Use stricter error string for implicit
	return type.
	* gcc.dg/cpp/digraphs.c: Declare puts.

From-SVN: r39608