add doxyfile to .Rbuildignore as R-devel now complains

eddelbuettel · eddelbuettel · commit 350906ad5789 · 2013-10-27T22:54:07.000Z
diff --git a/.Rbuildignore b/.Rbuildignore
@@ -10,3 +10,4 @@ vignettes/jss.bst
 inst/include/Rcpp/preprocessor
 inst/include/Rcpp/sugar/functions/impl
 vignettes/notyet
+doxyfile
