Deletes a key k and its corresponding value from a key-value pair.

Suppose the object's description is set to:

sound=on&time=now&position=<1,0,0>

When the function is called with:

llSetObjectDesc(wasKeyValueDelete("position", llGetObjectDesc()));

the object's description will be updated to:

sound=on&time=now

///////////////////////////////////////////////////////////////////////////
//    Copyright (C) 2014 Wizardry and Steamworks - License: CC BY 2.0    //
///////////////////////////////////////////////////////////////////////////
string wasKeyValueDelete(string k, string data) {
    if(llStringLength(data) == 0) return "";
    if(llStringLength(k) == 0) return "";
    integer i = llListFindList(
        llList2ListStrided(
            llParseString2List(data, ["&", "="], []), 
            0, -1, 2
        ), 
    [ k ]);
    if(i != -1) return llDumpList2String(
        llDeleteSubList(
            llParseString2List(data, ["&"], []),
        i, i), 
    "&");
    return data;
}

///////////////////////////////////////////////////////////////////////////
//    Copyright (C) 2014 Wizardry and Steamworks - License: CC BY 2.0    //
///////////////////////////////////////////////////////////////////////////
/// <summary>
///     Deletes a key-value pair from a string referenced by a key.
/// </summary>
/// <param name="key">the key to search for</param>
/// <param name="data">the key-value data segment</param>
/// <returns>a key-value pair string</returns>
private static string wasKeyValueDelete(string key, string data)
{
    List<string> output = new List<string>();
    foreach (string tuples in data.Split('&'))
    {
        string[] tuple = tuples.Split('=');
        if (!tuple.Length.Equals(2))
        {
            continue;
        }
        if (tuple[0].Equals(key, StringComparison.Ordinal))
        {
            continue;
        }
        output.Add(string.Join("=", tuple));
    }
    return string.Join("&", output.ToArray());
}

###########################################################################
##  Copyright (C) Wizardry and Steamworks 2015 - License: CC BY 2.0      ##
###########################################################################
function wasKeyValueDelete($key, $data) {
    $data = explode("&", $data);
    $data = array_filter(
        array_combine(
            array_map(
                function($o) {
                    return array_shift(explode("=", $o));
                }, 
                $data
            ), 
            array_map(
                function($o) {
                    return array_pop(explode("=", $o));
                }, 
                $data
            )
        )
    );
    if (array_key_exists($key, $data)) {
        unset($data[$key]);
    }
    array_walk($data,
        function(&$value, $key) {
            $value = $key."=".$value;
        }
    );
    return implode('&', $data);
}