* 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