C++ front-end: fix parsing of >> as closing template args

We also need to pop one token, not just replace the existing ones.

Author: tautschnig

regression/cpp/Templates4/main.cpp

@@ -0,0 +1,29 @@
+template <typename _Tp>
+struct __remove_cvref_t
+{
+};
+
+template <typename _Tp, typename _Up = __remove_cvref_t<_Tp>>
+struct __inv_unwrap
+{
+};
+
+template <typename...>
+struct __or_;
+
+template <bool _Cond, typename _Iftrue, typename _Iffalse>
+struct conditional
+{
+  typedef _Iftrue type;
+};
+
+template <typename _B1, typename _B2, typename _B3, typename... _Bn>
+struct __or_<_B1, _B2, _B3, _Bn...>
+  : public conditional<_B1::value, _B1, __or_<_B2, _B3, _Bn...>>::type
+{
+};
+
+int main(int argc, char *argv[])
+{
+  int x = 10 >> 1;
+}

regression/cpp/Templates4/test.desc

@@ -0,0 +1,8 @@
+CORE
+main.cpp
+
+^EXIT=0$
+^SIGNAL=0$
+--
+^warning: ignoring
+^CONVERSION ERROR$

src/cpp/parse.cpp

@@ -4017,8 +4017,8 @@ bool Parser::rTemplateArgs(irept &template_args)
       tk2.text='>';
       lex.Replace(tk2);
       lex.Insert(tk2);
+      lex.get_token();
       DATA_INVARIANT(lex.LookAhead(0) == '>', "should be >");
-      DATA_INVARIANT(lex.LookAhead(1) == '>', "should be >");
       return true;
 
     default: