* alpha.h (CPP_SPEC): Tidy.  Hook to cpp_cpu and cpp_subtarget.
        (CPP_SUBTARGET_SPEC): Default to empty string.
        (CPP_AM_*, CPP_IM_*, CPP_CPU_*, CPP_CPU_SPEC): New.
        (EXTRA_SPECS, SUBTARGET_EXTRA_SPECS): New.
        * alpha/elf.h (LD_SPEC): Use %(elf_dynamic_linker).
        * alpha/linux-elf.h (SUBTARGET_EXTRA_SPECS): New.
        (LIB_SPEC): Tidy.
        * alpha/linux.h (CPP_PREDEFINES): Tidy.
        * alpha/netbsd-elf.h (SUBTARGET_EXTRA_SPECS): New.
        * alpha/netbsd.h (CPP_PREDEFINES): Tidy.
        * alpha/osf.h (CPP_PREDEFINES): Remove bits subsumed by CPP_CPU_SPEC.
        * alpha/win-nt.h (CPP_PREDEFINES): Likewise.
        * alpha/vsf.h (CPP_PREDEFINES): Likewise.
        (CPP_SUBTARGET_SPEC): New.  Do this instead of overriding CPP_SPEC.
        * alpha/vxworks.h: Likewise.

From-SVN: r21311