flags.h, [...]: Remove flag_alias_check; optimization is now always enabled.

flags.h, [...]: Remove flag_alias_check; optimization is now always enabled.

        * flags.h, toplev.c, calls.c, alias.c: Remove flag_alias_check;
        optimization is now always enabled.
        * calls.c (expand_call): Recognize C++ operator new as malloc-like
        function.
        * alias.c (memrefs_conflict_p): Eliminate tests now done by
        base_alias_check.
        (*_dependence): Call canon_rtx before base_alias_check.
        (init_alias_once): New function to precompute set of registers which
        can hold Pmode function arguments.
        * rtl.h: Declare init_alias_once.
        * toplev.c (compile_file): Call init_alias_once.

From-SVN: r17227