Fix compilation on x86_64

[wmanley]

Compilation fails on x86_64 because there is a case statement switching on specific known architectures in configure.in:

machine=`($CC -dumpmachine)`
case $machine in
 i?86-*-*)  AC_SUBST(OBJECT_X86, 1)
        AC_SUBST(DOBJ_TARGET, "-DOBJECT_X86=1")
        AC_SUBST(ARCH, x86)
        if test -e "/lib/modules/`uname -r`/source"; then
           AC_SUBST(KERNELSOURCE, "/lib/modules/`uname -r`/source")
        fi;;
 mipsel-*-*)    AC_SUBST(OBJECT_4K, 1)
        AC_SUBST(DOBJ_TARGET, "-DOBJECT_4K=1")
        AC_SUBST(ARCH, mipsel-linux)
        AC_SUBST(CROSS_COMPILE, `echo $CC | sed 's/gcc$//'`);;
 mips-*)    AC_SUBST(OBJECT_4K, 1)
        AC_SUBST(DOBJ_TARGET, "-DOBJECT_4K=1")
        AC_SUBST(ARCH, mips-linux)
        AC_SUBST(CROSS_COMPILE, `echo $CC | sed 's/gcc$//'`);;
 sh4-*)     AC_SUBST(OBJECT_SH4, 1)
        AC_SUBST(DOBJ_TARGET, "-DOBJECT_SH4=1")
        AC_SUBST(ARCH, sh4-linux)
        AC_SUBST(CROSS_COMPILE, `echo $CC | sed 's/gcc$//'`);;
 *)         AC_MSG_ERROR("Unsupported target");;
esac

VQE-C should do something sensible on architectures which aren't listed here rather than just erroring out.