"<hicore>" sentinels.
        * gprof.c: Likewise.
        * cg_print.c (cg_print_function_ordering): Likewise.
        * alpha.c (alpha_find_call): Add check for return value of sym_lookup.
        * mips.c (mips_find_call): Likewise.
        * sparc.c (sparc_find_call): Likewise.
        * tahoe.c (tahoe_find_call): Likewise.
        * vax.c (vax_find_call): Likewise.