Add support for 32-bit and 64-bit PowerPC AIX core files.

Add support for 32-bit and 64-bit PowerPC AIX core files.

	* configure.ac (powerpc64-*-aix[5-9].*): Match powerpc64 running
	aix for core file support.
	* configure: Regenerate.
	* rs6000-core.c: Check for __ld_info64 if compiling 64-bit gdb.
	Added BFD64 check if we are using old core file format for 32-bit gdb.
	Set sizeof CORE_COMMONSZ appropriately in case of either new or
	old core file format.
	(read_hdr): Added BFD64 check for 64-bit support.
	(rs6000coff_core_p): Likewise.
	(rs6000coff_core_file_matches_executable_p): Likewise.
	(rs6000coff_core_file_failing_command): Likewise.
	(rs6000coff_core_file_failing_signal): Likewise.
	Add support for debugging core files generated by binaries in
	Large Memory model.
	(rs6000coff_core_p): If Large Memory Model is used, then the .data
	segment should start from BDATAORG which has been defined in the
	system header files.