bugc: combine thirteen fixes and additions - #368

This combines thirteen bugc fixes and additions, each already open and reviewed as its own pull request, into one change so they land together. The individual pull requests stay as the record of each change and will be closed in favour of this one.

Fixes:

• bugc: compile ! as a logical not #353 compile ! as a logical not (it compiled to a bitwise NOT)
• bugc: end each source range at its last token #362 end each source range at its last token (ranges included trailing whitespace and comments)
• bugc: slice a fixed-size bytes value by its bytes #357 slice a fixed-size bytes value by its bytes (a slice of a bytesN read the value as a memory address)
• bugc: hash the data of dynamic bytes and strings #360 hash the data of dynamic bytes and strings (at O0, keccak256 hashed the pointer word); builds on bugc: hash several value-type words with keccak256 #365's list of hashed values
• bugc: give a caller's call JUMP the invoke's arguments #354 give a caller's call JUMP the invoke's arguments (a frame lacked its arguments on its first step)
• bugc: list variables before a function's first statement #358 list variables before a function's first statement
• bugc: store a memory string's bytes when assigning it to storage #355 store a memory string's bytes when assigning it to storage (it stored the memory address)
• bugc: copy all of a slice's bytes #359 copy all of a slice's bytes (a slice copied at most one word)
• bugc: copy a struct read from storage into memory #361 copy a struct read from storage into memory (it crashed codegen)
• bugc: lay storage arrays out as Solidity does #364 lay storage arrays out as Solidity does (fixed-size arrays inline, dynamic arrays at keccak(slot) + i, narrow elements packed)

Additions:

• bugc: add block.prevrandao #363 block.prevrandao
• bugc: hash several value-type words with keccak256 #365 keccak256(a, b, …) over value-type words, equal to Solidity's keccak256(abi.encode(a, b, …))
• bugc: add push to dynamic arrays in storage #366 push on dynamic storage arrays; indexing at or past the length reverts with Panic(0x32)

Each pull request's changelog entry is kept as written.