* config.gcc (s390-*-linux-*, s390x-*-linux*): Switch to
new-style tm_file specification.  Specify correct tm_p_file,
md_file, and out_file for s390x.

* config/s390/linux.h, linux64.h:  Don't include other target
macro header files.  Now handled via tm_file.

* config/s390/linux.h, s390.h:  (IEEE_FLOAT, TARGET_IEEE_FLOAT,
TARGET_IBM_FLOAT): Move from linux.h to s390.h to ensure they
are defined before use.

From-SVN: r45685