Fix to Map caused by changes to hasSlicing.

import std.algorithm;
import std.range;

void main()
{
    auto N2 = sequence!"n"(cast(size_t)1).map!"a";
}

ceased to compile, because Map's opSlice won't work anymore over
infinite ranges, because the result can't be reassigned to the original.

std/algorithm.d

@@ -451,7 +451,7 @@ private struct MapResult(alias fun, Range)
         alias length opDollar;
     }
 
-    static if (hasSlicing!R)
+    static if (!isInfinite!R && hasSlicing!R)
     {
         static if (is(typeof(_input[ulong.max .. ulong.max])))
             private alias ulong opSlice_t;