Check alphabets for base32

[jbenet]

Make sure we track all the alphabets for base32 (that are very widely used)

[ghost]

https://dnscurve.org/in-implement.html

A byte string is interpreted as a number in little-endian form. Each 5-bit sequence of this number, from least significant to most significant, is encoded as one of the standard "digits" 0123456789bcdfghjklmnpqrstuvwxyz. A final sequence of fewer than 5 bits is zero-extended before encoding. Decoders must accept BCDFGHJKLMNPQRSTUVWXYZ as synonyms for bcdfghjklmnpqrstuvwxyz.

http://crockford.com/wrmg/base32.html

We chose a symbol set of 10 digits and 22 letters. We exclude 4 of the 26 letters: I L O U. When decoding, upper and lower case letters are accepted, and i and l will be treated as 1 and o will be treated as 0. When encoding, only upper case letters are used.

[DonaldTsang]

Other encodings

ABCDEFGHIJKLMNOPQRSTUVWXYZ234567 RFC4648
0123456789ABCDEFGHIJKLMNOPQRSTVW RFC2938
ybndrfg8ejkmcpqxot1uwisza345h769 Zbase32
0123456789ABCDEFGHJKMNPQRSTVWXYZ Crockford
0123456789ABCDEFGHIJKLMNOPQRSTUV base32hex
0123456789bcdefghjkmnpqrstuvwxyz Geohash