repr: print the name of structs
repr: remove trailing {} from unit-like structs
librustc: Add export_name attribute to specify symbol name.
Cleanup concurrency tests

In this commit I:
- removed unneeded heap allocations
- added extra whitespace to crowded expressions
- and removed unneeded syntax
auto merge of #8905 : sstewartgallus/rust/cleanup_tests, r=bblum

In this commit I:
- removed unneeded heap allocations
- added extra whitespace to crowded expressions
- and removed unneeded syntax

Also, CC @bblum although this change is fairly unobjectionable.
document why some tests are xfail-fast
hypothetical fix for #8865.
auto merge of #8899 : thestinger/rust/repr, r=huonw
small cleanup of previous commit with mucho comments.
auto merge of #8903 : luqmana/rust/en, r=thestinger

Fixes #8735.
auto merge of #8907 : pnkfelix/rust/fsk-fix-makefile-8865, r=thestinger

Fix #8865.
Modernized a few type names in rustc and syntax