add indexing with RangeInclusive in libcore and libcollections

src/libstd/lib.rs

@@ -233,6 +233,7 @@
 #![feature(fnbox)]
 #![feature(heap_api)]
 #![feature(hashmap_hasher)]
+#![feature(inclusive_range)]
 #![feature(int_error_internals)]
 #![feature(into_cow)]
 #![feature(lang_items)]