common.opt (fstack-protector): Initialize to -1.

common.opt (fstack-protector): Initialize to -1.

       * common.opt (fstack-protector): Initialize to -1.
        (fstack-protector-all): Likewise.
        (fstack-protector-strong): Likewise.
        (fstack-protector-explicit): Likewise.
        * configure.ac: Add --enable-default-ssp.
        * defaults.h (DEFAULT_FLAG_SSP): New.  Default SSP to strong.
        * opts.c (finish_options): Update opts->x_flag_stack_protect if it is
        -1.
        * doc/install.texi: Document --enable-default-ssp.
        * config.in: Regenerated.
        * configure: Likewise.

        * lib/target-supports.exp
        (check_effective_target_fstack_protector_enabled): New test.
        * gcc.target/i386/ssp-default.c: New test.

From-SVN: r227017