* configure.in: Set target_cpu_default2 for target_alias k6.
        * i386.h (TARGET_SWITCHES): Remove no-<cpu> entries.
        (CC1_CPU_SPEC): Likewise.
        (CPP_CPU_DEFAULT_SPEC): Streamline definition.  Add K6 version.
        (CPP_K6_SPEC): New.
        (CPP_CPU_SPEC): Add K6 variant.
        (EXTRA_SPECS): Likewise.

Co-Authored-By: Richard Henderson <rth@cygnus.com>

From-SVN: r26341