Add tasks for all the new languages

Task/Longest-string-challenge/Phix/longest-string-challenge-1.phix

@@ -0,0 +1,23 @@
+integer fn = open(command_line()[2],"r") -- (reading the source file)
+
+function allx(string line)
+    line[1..-1] = 'x'
+    return line
+end function
+
+function longest(string mask)
+object line = gets(fn)
+string newmask
+    if atom(line) then return mask end if
+    newmask = allx(line)
+    if not match(mask,newmask) then return longest(mask) end if
+    mask = longest(newmask)
+    if match(mask,newmask) then
+        puts(1,line)
+    end if
+    return mask
+end function
+
+?longest("x")
+
+close(fn)

Task/Longest-string-challenge/Phix/longest-string-challenge-2.phix

@@ -0,0 +1,12 @@
+function longest(integer l)
+object line = gets(fn)
+    if line=-1 then return l end if
+    if l>length(line) then return longest(l) end if
+    l = longest(length(line))
+    if l=length(line) then
+        puts(1,line)
+    end if
+    return l
+end function
+
+?longest(0)

Task/Longest-string-challenge/Sidef/longest-string-challenge.sidef

@@ -0,0 +1,9 @@
+var l = '';  # Sample longest string seen.
+var a = '';  # Accumulator to save longest strings.
+
+STDIN.each { |n|
+    n.substr(l.len) ? (a = n; l = n)
+                    : (!l.substr(n.len) && a.concat!(n));
+}
+
+print a;