add operators == and != against SEXP to String class (rounds off #372)

Author: eddelbuettel

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: Rcpp
 Title: Seamless R and C++ Integration
-Version: 0.12.0.5
-Date: 2015-08-31
+Version: 0.12.0.9
+Date: 2015-09-09
 Author: Dirk Eddelbuettel, Romain Francois, JJ Allaire, Kevin Ushey, 
  Qiang Kou, Douglas Bates and John Chambers
 Maintainer: Dirk Eddelbuettel <[email protected]>

inst/include/Rcpp/String.h

@@ -438,6 +438,14 @@ namespace Rcpp {
             return strcmp( get_cstring(), other.get_cstring() ) > 0;
         }
 
+        bool operator==( SEXP other ) const {
+            return get_sexp() == other;
+        }
+
+        bool operator!=( SEXP other ) const {
+            return get_sexp() != other;
+        }
+
     private:
 
         /** the CHARSXP this String encapsulates */