samples: add Terra samples

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

samples/Terra/enumc.t

@@ -0,0 +1,14 @@
+C = terralib.includecstring [[
+    enum  Foo {
+        A_VALUE = -1,
+        B_VALUE = 4,
+        C_VALUE = 2 << 1,
+        D_VALUE = (1 << 31) - 1,
+        E_VALUE = (1 << 44)
+    };
+]]
+assert(C.A_VALUE == -1)
+assert(C.B_VALUE == 4)
+assert(C.C_VALUE == 4)
+assert(C.D_VALUE == 2147483647)
+assert(C.E_VALUE == -2147483648)