2001-02-26  D.J. Barrow <djbarrow@de.ibm.com,barrow_dj@yahoo.com>
	* s390-nat.c New file Added for S/390 31 & 64 bit target.
	* s390-tdep.c Likewise.
	* config/s390/nm-linux.h Likewise.	 
	* config/s390/s390x.mt Likewise.
	* config/s390/tm-linux.h  Likewise.  
	* config/s390/xm-linux.h Likewise
	* config/s390/s390.mh Likewise.
	* config/s390/s390.mt Likewise.
	* config/s390/tm-s390.h Likewise.
        * config.in Added definitions for S/390 31 & 64 bit target.
	* configure.host Likewise.
	* configure.in Likewise.
	* configure.tgt  Likewise.

        * gdbarch.sh Added 2 definitions to the input table
	allow_null_function, this definition is set to an
	non empty string if it is okay for the gdbarch function
	to be null.
	null_function_default_retval, this definiton is the
	default return value for a undefined function
	(i.e. allow_null_function is defined ).
	Added new macros required for S/390
	INIT_FRAME_PC_FIRST
	CANNOT_STORE_REGISTER
	CANNOT_FETCH_REGISTER
	ADDR_BITS_REMOVE
	EXTRACT_STRUCT_VALUE_ADDRESS_P        

	Improved the behaviour of the following macros.
	PUSH_RETURN_ADDRESS 
	added allow null function so default behaviour would be correct.
	EXTRACT_STRUCT_VALUE_ADDRESS
	added check for EXTRACT_STRUCT_VALUE_ADDRESS_P
	CALL_DUMMY_BREAKPOINT_OFFSET

	* core-aout.c added check for CANNOT_FETCH_REGISTER
	in fetch_core_registers.
	* arch-utils.c added check for BFD_ENDIAN_UNKNOWN
	in set_endian_from_file.