samples: add Terra samples

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

samples/Terra/canon2.t

@@ -0,0 +1,41 @@
+local C = terralib.includecstring [[
+    typedef union {
+            float v[2];
+            struct {
+                float x;
+                float y;
+            };
+    } float2;
+    static float2 a;
+    void doit() {
+        a.x = 4;
+        a.y = 5;
+    }
+    float2* what() { return &a; }
+]]
+
+C.float2:printpretty()
+
+local anonstructgetter = macro(function(name,self)
+    for i,e in pairs(self:gettype():getfields()) do
+        if e.key:match("_%d+") and e.type:getfield(name) then
+            return `self.[e.key].[name]
+        end
+    end 
+    error("no field "..name.." in struct of type "..tostring(T))
+end)
+
+C.float2.metamethods.__entrymissing = anonstructgetter
+
+terra foo(pa : &C.float2)
+    var a = @C.what()
+    return a.v[0],a.v[1],a.x,a.y
+end
+
+C.doit()
+
+local a = foo(C.what())
+assert(4 == a._0)
+assert(5 == a._1)
+assert(4 == a._2)
+assert(5 == a._3)