feat(core, abi): support shorthand function declarations

[shekhirin]

Motivation

See #446

Solution

Support shorthand function declarations

[gakonst]

This is great. Thank you. Paging @mattsse in case he's available to review this, since he wrote the parser, otherwise I'll try to take a closer look tomorrow.

[shekhirin]

Another thing that may worth filing a new issue: redesign human readable ABI parsing, so it doesn't split the strings 9999 times but iterate the tokens instead 😄

[mattsse]

Definitely, when I first wrote this I used the internal ethabi parser as the basis for that.
Tokenization would be much nicer, but at least the human readable abi does only add to compile-time in abigen!
+1 for follow up issue, parts of solang could be useful for that,

[mattsse]

awesome