__p_rcode_syms is declared as external in resolv.conf, so it cannot be
redeclared as static in res_debug.c.

Make p_rcode_syms global and add it to Symbol map. The rest of
p_??_syms are already global.

Choice of FBSD_1.0 version for these debug symbols seems strange and
should be revisited before symbol versioning is enabled for libc.so.7.