Rolling up PRs in the queue

Closes #12474 (rustc: Don't error on the rlib symlinks) r=brson
Closes #12475 (Use lines_any() when parsing output form "ar") r=brson
Closes #12476 (Remove some obsolete ignored tests) r=alexcrichton
Closes #12481 (Make .swap_remove return Option<T>) r=brson
Closes #12485 (Remove some non-essential trait re-exports from the prelude.) r=brson
Closes #12489 (Handle multibyte characters in source files better) r=alexcrichton
Closes #12494 (Mark by-value parameters that are passed on the stack as nocapture) r=nmatsakis
Closes #12497 (syntax: allow stmt/expr macro invocations to be delimited by {}) r=alexcrichton
Closes #12508 (Match binding is assignment) r=nmatsakis
Closes #12513 (Run the travis build as one large command) r=huonw
Closes #12515 (Update source code layout in src/) r=alexcrichton
Closes #12521 (Tutorial: Add std::num::sqrt to the example) r=cmr
Closes #12529 (test: single-variant enum can't be dereferenced) r=huonw