uinsert - Inserts a character in a string. Allegro game programming library.
int uinsert(char *s, int index, int c);
Inserts the character `c' at the specified `index' in the string, sliding the
rest of the data along to make room. If `index' is negative, it counts
backward from the end of the string. Example:
uinsert(text_string, 0, prefix_letter);
Returns the number of bytes by which the trailing part of the string was moved.
uoffset(3alleg4), ugetat(3alleg4), usetat(3alleg4),