usetat - Replaces a character in a string. Allegro game programming library.
int usetat(char *s, int index, int c);
Replaces the character at the specified index in the string with value `c',
handling any adjustments for variable width data (ie. if `c' encodes to a
different width than the previous value at that location). If `index' is
negative, it counts backward from the end of the string. Example:
usetat(text_string, 2, letter_a);
Returns the number of bytes by which the trailing part of the string was moved.
This is of interest only with text encoding formats where characters have a
variable length, like UTF-8.
uoffset(3alleg4), ugetat(3alleg4), uinsert(3alleg4),