append for #to_bson(encoded = ''.force_encoding(BINARY))
string.to_bson_string(encoded) appends bson string to encoded, encode_string_with_placeholder
string.to_bson_string(encoded) appends bson string to encoded

symbol.to_bson_cstring(encoded) appends bson cstring to encoded
encode_binary_data_with_placeholder
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
symbol to_bson_cstring tweak & memo doc keys in progress
bench_test for Array index map and doc key memo