samples: add Terra samples

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

samples/Terra/ifelse.t

@@ -0,0 +1,17 @@
+
+terra foo(a : int)
+	return terralib.select(a > 0, 1,-1)
+end
+
+
+terra foo2(a : int)
+	var c = vector(a > 0, a > 1, a > 2)
+	var d = terralib.select(c,vector(1,2,3),vector(4,5,6))
+	return d[0], d[1], d[2]
+end
+local test = require("test")
+
+test.eq(foo(1),1)
+test.eq(foo(-1),-1)
+
+test.meq({1,5,6},foo2(1))