* config/s390/s390.h (TARGET_DEFAULT_BACKCHAIN): New define.
	(TARGET_DEFAULT): Use symbolic values.
	* config/s390/tpf.h (TARGET_DEFAULT_BACKCHAIN): Redefine.
	(TARGET_DEFAULT): Use symbolic values.
	* config/s390/s390.c (s390_backchain_string): Initialize to
	TARGET_DEFAULT_BACKCHAIN.

From-SVN: r88763