* 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.