Restore CPP11_UNWIND for textshaping

r-lib/textshaping#47

Author: DavisVaughan

inst/include/cpp11/declarations.hpp

@@ -30,6 +30,11 @@ T& unmove(T&& t) {
 }
 }  // namespace cpp11
 
+// We would like to remove this, since all supported versions of R now support proper
+// unwind protect, but some groups rely on it existing, like textshaping:
+// https://github.com/r-lib/cpp11/issues/414
+#define CPP11_UNWIND R_ContinueUnwind(err);
+
 #define CPP11_ERROR_BUFSIZE 8192
 
 #define BEGIN_CPP11                   \