* config/alpha/linux.h, config/arm/linux-elf.h, config/i370/linux.h,

    * config/alpha/linux.h, config/arm/linux-elf.h, config/i370/linux.h,
        config/i386/linux-aout.h, config/i386/linux-oldld.h,
        config/i386/linux.h, config/i386/linux64.h, config/ia64/linux.h,
        config/m68k/linux-aout.h, config/m68k/linux.h, config/mips/linux.h,
        config/pa/pa-linux.h, config/pj/linux.h, config/s390/linux.h,
        config/sh/linux.h, config/sparc/linux-aout.h, config/sparc/linux.h,
        config/sparc/linux64.h, config/xtensa/linux.h (CPP_PREDEFINES):
        Define __gnu_linux__, not gnu_linux.
        * config/rs6000/sysv4.h (CPP_OS_GNU_SPEC): Likewise for gnu_hurd.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@52329 138bc75d-0d04-0410-961f-82ee72b054a4