add string concat test to basic.zig from misc.zig!

This means it is passing in stage2!

test/behavior/basic.zig

@@ -162,3 +162,7 @@ fn fA() []const u8 {
 fn fB() []const u8 {
     return "b";
 }
+
+test "string concatenation" {
+    try expect(mem.eql(u8, "OK" ++ " IT " ++ "WORKED", "OK IT WORKED"));
+}

test/behavior/misc.zig

@@ -40,10 +40,6 @@ test "constant equal function pointers" {
 
 fn emptyFn() void {}
 
-test "string concatenation" {
-    try expect(mem.eql(u8, "OK" ++ " IT " ++ "WORKED", "OK IT WORKED"));
-}
-
 test "array mult operator" {
     try expect(mem.eql(u8, "ab" ** 5, "ababababab"));
 }