Finds an element in the queue @array, either by comparing every element with @func or by looking up @data if no compare function @func is provided, and returning the index of the found element.
comparison function, or %NULL to find @data by value
data for comparison function
Index of the found element or -1 if nothing was found.
1.2
See Implementation
Finds an element in the queue @array, either by comparing every element with @func or by looking up @data if no compare function @func is provided, and returning the index of the found element.