libstdc++: Fix narrowing conversions for 16-bit size_t [PR105681]

libstdc++: Fix narrowing conversions for 16-bit size_t [PR105681]

On a 16-bit target such as msp430 we get errors about narrowing long
values to size_t, which is only 16-bit. When --enable-libstdcxx-pch is
used the <bits/extc++.h> header breaks the build because of these
narrowing errors.

libstdc++-v3/ChangeLog:

	PR libstdc++/105681
	* include/ext/pb_ds/detail/resize_policy/hash_prime_size_policy_imp.hpp:
	Limit ga_sizes array to values that fit in size_t.
	* include/ext/random [__SIZE_WIDTH < 32] (sfmt86243)
	(sfmt86243_64, sfmt132049, sfmt132049_64, sfmt216091)
	(sfmt216091_64): Do not declare.

(cherry picked from commit 367740bf6d3a6627798b3955e5d85efc7549ef50)