* cmd/evm: improve flags handling
This fixes some issues with flags in cmd/evm. The supported flags did not
actually show up in help output because they weren't categorized. I'm also
adding the VM-related flags to the run command here so they can be given
after the subcommand name. So it can be run like this now:
./evm run --code 6001 --debug
* cmd/evm: enable all forks by default in run command
The default genesis was just empty with no forks at all, which is annoying because
contracts will be relying on opcodes introduced in a fork. So this changes the default to
have all forks enabled.
* core/asm: fix some issues in the assembler
This fixes minor bugs in the old assembler:
- It is now possible to have comments on the same line as an instruction.
- Errors for invalid numbers in the jump instruction are reported better
- Line numbers in errors were off by one
* core/asm: Fix encoding of pushed labels
EVM uses big-endian byte-order, so to pad a label value to 4 bytes,
zeros must be added to the front, not the end.
* core/asm: Fix PC calculations when a label is pushed
Incrementing PC by 5 is only correct if the label appears after a jump,
in which case there is an implicit push. When it appears after an explicit
push, PC should only be incremented by 4.
* core/asm: Allow JUMP with no argument
This way, a label can be pushed explicitly, or loaded from memory to
implement a jump table.
