Bump recursion_limit in a few places

This is needed to get rustdoc to succeed on `dist-x86_64-linux-alt`

Author: Aaron1011

Diff for: compiler/rustc_builtin_macros/src/lib.rs

@@ -11,6 +11,7 @@
 #![feature(or_patterns)]
 #![feature(proc_macro_internals)]
 #![feature(proc_macro_quote)]
+#![recursion_limit = "256"]
 
 extern crate proc_macro;
 

Diff for: compiler/rustc_parse/src/lib.rs

@@ -6,6 +6,7 @@
 #![feature(or_patterns)]
 #![feature(box_syntax)]
 #![feature(box_patterns)]
+#![recursion_limit = "256"]
 
 use rustc_ast as ast;
 use rustc_ast::token::{self, Nonterminal};

Diff for: compiler/rustc_session/src/lib.rs

@@ -1,6 +1,7 @@
 #![feature(crate_visibility_modifier)]
 #![feature(once_cell)]
 #![feature(or_patterns)]
+#![recursion_limit = "256"]
 
 #[macro_use]
 extern crate bitflags;