Don't emit empty string concatenations for interpolated strings, see comment in #159

Don't add `+ ""` or `"" + ` when interpolations are at the very beginning or end of the string, or adjacent.

Author: hsutter

source/cppfront.cpp

@@ -1031,6 +1031,16 @@ class cppfront
         }
         ret += text.substr(current_start);
 
+        //  Trim any stray "" pieces
+        auto match = std::string::size_type{};
+        while ((match = ret.find("\"\" + ", match)) != ret.npos) {
+            ret.replace(match, 5, "");
+        }
+        match = 0;
+        while ((match = ret.find(" + \"\"", match)) != ret.npos) {
+            ret.replace(match, 5, "");
+        }
+
         return ret;
     }