Zero-length static array is null, unlike in dmd

LDC treats zero-length arrays differently from dmd:

void test(int[] data)
  in { assert(data, "data must be non-null."); }
  body { }

void main() {
  import std.stdio;
  int[1] data1;
  writeln(data1); // [0]
  test(data1); // Passes
  int[0] data0;
  writeln(data0); // []
  test(data0); // Passes with dmd 2.066.1, asserts with ldc2 0.15.1
}
