libstdc++: Fix pool resource build errors for H8 [PR107801]

The array of pool sizes was previously adjusted to work for msp430-elf
which has 16-bit int and either 16-bit size_t or 20-bit size_t. The
largest pool sizes were disabled unless size_t has more than 20 bits.

The H8 family has 16-bit int but 32-bit size_t, which means that the
largest sizes are enabled, but 1<<15 produces a negative number that
then cannot be narrowed to size_t.

Replace the test for 32-bit size_t with a test for 32-bit int, which
means we won't use the 4kiB to 4MiB pools for targets with 16-bit int
even if they have a wider size_t.

libstdc++-v3/ChangeLog:

	PR libstdc++/107801
	* src/c++17/memory_resource.cc (pool_sizes): Disable large pools
	for targets with 16-bit int.