verify.cc (_Jv_BytecodeVerifier::linked_utf8): New structure.
* verify.cc (_Jv_BytecodeVerifier::linked_utf8): New structure.
(_Jv_BytecodeVerifier::utf8_list): New field.
(_Jv_BytecodeVerifier::_Jv_BytecodeVerifier): Initialize it.
(_Jv_BytecodeVerifier::~_Jv_BytecodeVerifier): Free it.
(_Jv_BytecodeVerifier::make_utf8_const): New method.
(_Jv_BytecodeVerifier::get_one_type): Use it.
(_Jv_BytecodeVerifier::type::merge): When using local semantics,
if the destination type is already unsuitable then we didn't
change.