fix bob syntax errors

repro (darwin):
$ m -s && TEST_VERBOSE=1 pb examples/bench.pl -bob -nul -pic -1opt

bob/perfect -NPs phash </usr/share/dict/words  >/dev/null
/usr/bin/clang -shared  -Ibob -I. -O3  -pipe -Os  -fno-common -DPERL_DARWIN -I/opt/local/include -no-cpp-precomp -fno-strict-aliasing -fstack-protector -I/usr/local/include -I/opt/local/include    -o phash_hash.bundle phash_hash.c bob/lookupa.c
phash_hash.c:4181:38: error: use of undeclared identifier 'tab'
  rsl = ((state[0]&0x3ffff)^scramble[tab[state[1]&0xffff]]);