-m31 -mzarch uses 64 as word size instead of 32.  This must not affect
the Address type definition which is based on Memory_Size.

gcc/ada/ChangeLog:

2017-04-04  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	* system-linux-s390.ads: Use Long_Integer'Size to define
	Memory_Size.

From-SVN: r246678