HLL::Grammar and HLL::Actions

HLL::Grammar predefined rules and tokens:

<EXPR>       - operator precedence parser
<ws>         - whitespace and #-comments
<decint>     - decimal integer
<hexint>     - hexadecimal integer
<octint>     - octal integer
<binint>     - binary integer
<integer>    - non-negative integer, incl 0x..., 0b..., etc.
<dec_number> - decimal number with fractional or exponential part
<quote_EXPR> - quoted expressions
<quote_escape> - backslash escapes \n, \r, \t, \x, etc.

Subclasses can easily override these

Defaults allow prototyping a language quickly.