Better alphabets

[jimd1989]

Rather than parsing a normal func like < and an "extended" func like @<, and presumably extended extended funcs like @@<, each with their own enum cases, can probably go the J route and combine them all into one alphabet like <, <.. . isn't used in functions at the moment in order to make parsing decimal numbers dead easy, but the logic of adding it would not be much tougher than the existing @ notation. The only ambiguity would be something like <.5, which should favor the function. There are already certain instances that necessitate whitespace anyway.

Can be combined into one alphabet with something like

VM_LESS_THAN = '<',
VM_FLOOR = '<' | ('.' << 8)

etc.

This would remove the need for redundant f and g fields in the VmCell union, which currently segregate normal functions and extended functions respectively for pattern matching warning purposes.