Bird 2.0.0: configure --with-protocols bug

[Luis Ressel]

Hello *,

I just discovered that bird's ./configure --with-protocols is buggy. If
radvd is excluded from the protocol list, make fails with the error

bison  -dv -pcf_ -b obj/conf/cf-parse obj/conf/cf-parse.y
obj/conf/cf-parse.y:3955.4-12: error: symbol PREFERRED is used, but is
not defined as a token and has no rules
    PREFERRED ipa { kif_set_preferred($2); }
    ^^^^^^^^^
make: *** [conf/Makefile:23: obj/conf/cf-parse.tab.c] Error 1

Regards,
Luis Ressel