* config.gcc: Set default for xmake_file at top, not bottom.
	Change places that set xmake_file to "none" to set to the
	empty string instead, or remove them entirely if there is no
	default xmake_file for this cpu_type.  Remove references to
	deleted files.

	* config/x-lynx, config/convex/x-convex, config/elxsi/x-elxsi,
	config/i386/x-isc, config/i386/x-isc3, config/i386/x-ncr3000,
	config/i386/x-next, config/i386/x-sco, config/i386/x-sysv3,
	config/i386/x-vsta, config/i860/x-sysv4, config/m68k/x-amix,
	config/m68k/x-apollo68, config/m68k/x-ccur, config/m68k/x-crds,
	config/m68k/x-hp2bsd, config/m68k/x-mot3300, config/m68k/x-mot3300-gas,
	config/m68k/x-tower, config/m88k/x-sysv4, config/mips/x-dec-osf1,
	config/mips/x-sni-svr4, config/mips/x-ultrix, config/romp/x-mach,
	config/romp/x-romp, config/rs6000/x-beos, config/rs6000/x-lynx,
	config/rs6000/x-mach, config/rs6000/x-sysv4, config/sparc/x-sysv4:
	Delete.

	* config/a29k/x-unix, config/i386/x-aix, config/i386/x-osf1elf,
	config/i386/x-osfrose, config/m68k/x-dpx2, config/mips/x-iris3,
	config/mips/x-mips, config/mips/x-osfrose, config/mips/x-sony,
	config/mips/x-sysv, config/rs6000/x-aix31:
	Just set CLIB to -lld or -lmld, as appropriate.

	* config/arm/x-riscix, config/i370/x-oe, config/i386/x-dgux,
	config/i386/x-sco4, config/i386/x-sco5, config/m68k/x-hp320,
	config/m68k/x-hp320g, config/m68k/x-next, config/m88k/x-dgux,
	config/mips/x-iris, config/pa/x-pa:
	Just set (some of) FIXPROTO_DEFINES, STMP_FIXPROTO,
	OTHER_FIXINCLUDES_DIRS.

	* config/i386/x-djgpp: Don't set LN or LN_S.
	* config/m88k/x-dolph: Don't define __m88k__.
	* config/m88k/x-tekXD88: Don't set AR_FLAGS.
	* config/pa/x-pa-mpeix: Just set up quadlib.asm.
	* config/i860/fx2800.h: No need to #undef SVR4.

	38 x-host fragments remain, 2 x-cpu.

From-SVN: r41181