Auto merge of #50275 - kennytm:rollup, r=kennytm

Auto merge of #50275 - kennytm:rollup, r=kennytm

Rollup of 7 pull requests

Successful merges:

 - #49707 (Add "the Rustc book")
 - #50222 (Bump bootstrap compiler to 2018-04-24)
 - #50227 (Fix ICE with erroneous `impl Trait` in a trait impl)
 - #50229 (Add setting to go to item if there is only one result)
 - #50231 (Add more doc aliases)
 - #50246 (Make dump_{alloc,allocs,local}() no-ops when tracing is disabled.)
 - #49894 (Rename InternedString to LocalInternedString and introduce a new thread-safe InternedString)

Failed merges: