Add c_std and cpp_std properties.

Test: Checked showcommands ouput for each setting.
Bug: None
Change-Id: Ibe02352f19ca2777b9a419136270e5c4390f1149
diff --git a/cc/config/global.go b/cc/config/global.go
index e248040..e254a1c 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -65,9 +65,11 @@
 		"-w",
 	}
 
-	CStdVersion      = "gnu99"
-	CppStdVersion    = "gnu++14"
-	GccCppStdVersion = "gnu++11"
+	CStdVersion               = "gnu99"
+	CppStdVersion             = "gnu++14"
+	GccCppStdVersion          = "gnu++11"
+	ExperimentalCStdVersion   = "gnu11"
+	ExperimentalCppStdVersion = "gnu++1z"
 )
 
 var pctx = android.NewPackageContext("android/soong/cc/config")