rustdoc: Process markdown pages in sequence. Closes #2484

Author: brson

src/rustdoc/markdown_pass.rs

@@ -83,7 +83,9 @@ fn write_markdown(
     doc: doc::doc,
     +writer_factory: writer_factory
 ) {
-    do par::map(doc.pages) |page| {
+    // FIXME #2484: There is easy parallelism to be had here but
+    // we don't want to spawn too many pandoc processes
+    do doc.pages.map |page| {
         let ctxt = {
             w: writer_factory(page)
         };