/* Return information about charsets in the text at PTR of NBYTES
bytes, which are NCHARS characters. The value is:
- 0: Each character is represented by one byte. This is alwasy
+ 0: Each character is represented by one byte. This is always
true for unibyte text.
1: No charsets other than ascii eight-bit-control,
eight-bit-graphic, and latin-1 are found.