librustc: De-`@mut` the short names cache
librustc: De-`@mut` the `needs_unwind_cleanup_cache`
librustc: De-`@mut` the `tc_cache`
librustc: De-`@mut` `monomorphized` in the crate context
librustc: De-`@mut` the `monomorphizing` field in `CrateContext`
librustc: De-`@mut` `CrateContext::item_vals`
librustc: De-`@mut` `item_symbols`
librustc: Remove unused field `enum_sizes` from the crate context
librustc: Remove unused `discrim_symbols` field from the crate context
librustc: De-`@mut` `CrateContext::vtables`.
librustc: De-`@mut` `CrateContext::const_cstr_cache`.
librustc: De-`@mut` `RefCell::const_globals`.
librustc: De-`@mut` `const_values`.
librustc: De-`@mut` `CrateContext::extern_const_values`
librustc: De-`@mut` the `impl_method_cache`
librustc: De-`@mut` `CrateContext::module_data`
librustc: De-`@mut` `lltypes`.
librustc: De-`@mut` `CrateContext::llsizingtypes`
librustc: De-`@mut` `CrateContext::adt_reprs`
librustc: De-`@mut` `CrateContext::type_hashcodes`