flow.c: Grammar check and clarify a lot of comments.

flow.c: Grammar check and clarify a lot of comments.

        * flow.c: Grammar check and clarify a lot of comments.
        (try_simplify_condjump): Rename variables to be clearer.
        (try_forward_edges): Skip complex and fallthru edges.
        Rearrange tests to avoid duplicate checks.
        (flow_find_cross_jump): Likewise.
        (outgoing_edges_match): Allow match if neither branch has
        probability data.  Loosen probability match to 5%.
        (try_crossjump_to_edge): Hoist repeated indirection into
        local variables.
        (try_crossjump_bb): Don't check complex edges.  Eliminate
        redundant crossjump tests.
        (try_optimize_cfg): Fix use of bool.  Reorganize cheaper
        checks before more expensive checks.

From-SVN: r44257