* doc(host) Fix the `Externals` example
The example is missing two things:
* `index` is computed but not used,
* `check_signature` is never used.
This patch tries to fix that.
* doc(host) Fix `check_signature` example
This also allows `Instruction` to be `Copy`, which massively speeds
up `<Instructions as Clone>::clone` since it can now just `memcpy`
the bytes using SIMD instead of having to switch on every single
element. I haven't looked at the disassembly of `InstructionIter::next`
yet, it could be that there are even more improvements yet to be gained
from either:
* Only doing work on `BrTable` (this might already be the case depending
on the whims of the optimiser)
* Using `unsafe` to make it a noop (we really don't want to do this,
obviously, since it means that `Instructions` has to be immovable)
* add default-enabled std feature
* use parity-wasm/std feature only if std is enabled
* drop dependency on std::io
* use hashmap_core instead of std::collections::HashMap
* disable std::error in no_std
* core and alloc all the things
* mention no_std in readme
* add no_std feature and use hashmap_core only on no_std
* rename the no_std feature to core
* drop dependency on byteorder/std
* simplify float impl macro
* remove some trailing whitespace
* use libm for float math in no_std
* add note about no_std panics of libm to readme
* Embed nan-preserving-float crate.
* Add no_std check to the Travis CI config
* add missing dev-dependency
* Hide Instructions implementation behind an iterator
* Hide instruction encoding behind isa::Instructions::push()
* Consistently use u32 for program counter storage
* Refer to instructions by position rather than index
Sergey Pepyakin
Elichai Turkel
Leonardo Yvens
Arkadiy Paronyan
Sergei Pepyakin
Jef
Ivan Enderlin
Eric Findlay
Wei Tang
Julius Rakow
Will Glynn
Tobias Bucher
Guanqun Lu