Remove fk_anon
rewrite of shootout-fasta.rs

improvements:
 - no managed box
 - no virtual calls
 - no useless copy
 - optimizations (bisect is slower, limit tests, BufferedWriter...)
 - pass shootout test
 - should be as fast as the best official test

Thanks to @cmr and @eddyb for their help!
Use libdir() instead of hard coded string. Fixes #10903
Update documentation for new `pkgid` attribute.
auto merge of #10935 : sanxiyn/rust/fk-anon, r=pcwalton
auto merge of #10933 : TeXitoi/rust/shootout-fasta-rewrite, r=alexcrichton

improvements:
 - no managed box
 - no virtual calls
 - no useless copy
 - optimizations (bisect is slower, limit tests, BufferedWriter...)
 - pass shootout test
 - 10 times faster
auto merge of #10938 : jhasse/rust/patch-rustpkg, r=alexcrichton

rustpkg assumes library files to be in a directory called `lib`, but on Windows they are instead in the `bin` directory. This patch changes nothing on Unix system, since `libdir()` returns `"lib"` there.
auto merge of #10944 : metajack/rust/pkgid-docs, r=cmr