libstdc++: Include <typeinfo> even for -fno-rtti [PR 97758]

The std::function code now uses std::type_info* even when RTTI is
disabled, so it should include <typeinfo> unconditionally. Without this,
Clang can't compile <functional> with -fno-rtti (it works with GCC
because std::type_info gets declared automatically by the compiler).

libstdc++-v3/ChangeLog:

	PR libstdc++/97758
	* include/bits/std_function.h [!__cpp_rtti]: Include <typeinfo>.

libstdc++-v3/include/bits/std_function.h

@@ -36,9 +36,7 @@
 # include <bits/c++0x_warning.h>
 #else
 
-#if __cpp_rtti
-# include <typeinfo>
-#endif
+#include <typeinfo>
 #include <bits/stl_function.h>
 #include <bits/invoke.h>
 #include <bits/refwrap.h>