Read a character by its Unicode name or hex number string.
Display PROMPT and read a string that represents a character by its
Unicode property `name' or `old-name'.
This function returns the character as a number.
You can type a few of the first letters of the Unicode name and
use completion. If you type a substring of the Unicode name
preceded by an asterisk `*' and use completion, it will show all
the characters whose names include that substring, not necessarily
at the beginning of the name.
This function also accepts a hexadecimal number of Unicode code
point or a number in hash notation, e.g. #o21430 for octal, #x2318 for hex, or #10r8984 for decimal.