Hot/cold attributes for labels.

Hot/cold attributes for labels.

gcc/
        * doc/extend.texi (attribute): Document hot/cold for labels.
        * predict.c (tree_estimate_probability_bb): Handle hot/cold
        attributes on user labels.
        * predict.def (PRED_HOT_LABEL, PRED_COLD_LABEL): New.
gcc/c-family/
        * c-common.c (handle_hot_attribute): Allow labels.
        (handle_cold_attribute): Likewise.
gcc/testsuite/
        * gcc.dg/attr-hotcold-1.c: New.
        * gcc.dg/tree-ssa/attr-hotcold-2.c: New.

From-SVN: r189898