resurect shootout-mandelbrot.rs

Changes:
* add licence;
* remove usage of libc and unsafe;
* use BufferedWriter to improve performance;
* use a DummyWriter to cancel binary output in test.
Clarrify the message for test mode and use u8 instead of i8 for storing bits
Prettier long string breaking.
Add doc comment for extra::url::query_to_str
auto merge of #10531 : TeXitoi/rust/mandelbrot-resurected, r=cmr

Changes:
* add licence;
* remove usage of libc and unsafe;
* use BufferedWriter to improve performance;
* use a DummyWriter to cancel binary output in test.
auto merge of #10532 : dhodder/rust/master, r=alexcrichton

Hello.  This is just a tiny doc update -- I'm new here, so apologies if I'm doing it wrong.
Add a test for #6976

Closes #6976
Better error message when using vectors in statics

Closes #10487
auto merge of #10511 : cmr/rust/addtests, r=huonw

Commit messages have all
Fixed uses of get() to unwrap() in doc examples in std::iter
Fixed docs for advance() in Iterator trait
Fixed whitespace
Merging