samples: add Terra samples

source: https://github.com/zdevito/terra/tree/master/tests

samples/Terra/indexingbug.t

@@ -0,0 +1,31 @@
+arr = terralib.new(int[256])
+
+arr[252] = 12
+
+terra foo(arr : &int)
+  var idx = [uint8](252)
+  return arr[idx]
+end
+
+terra foo2(arr : &int)
+  var idx = [uint8](252)
+  return @(arr + idx)
+end
+
+terra foo3(arr : &int)
+  var idx = [int8](-3)
+  arr = arr + 255
+  return @(arr + idx)
+end
+
+
+terra foo4(arr : &int)
+  var idx = [int8](-3)
+  arr = arr + 255
+  return arr[idx]
+end
+
+assert(foo2(arr) == 12)
+assert(foo(arr) == 12)
+assert(foo3(arr) == 12)
+assert(foo4(arr) == 12)