Add named `INT` and `FLT`.

[python-processing-unit]

Add named INT and FLT.

Symbols, parameters, and return types of type INT and FLT (referred to as numbers for convenience) MAY now specify a base with the form TYPE{base}, where the base is written as an INT.

Named numbers with different bases are treated as different types, but are all considered part of their parent types (INT or FLT). A coerced type parameter that uses named numbers converts numbers to the correct type.

Signatures now include bases in the type annotation for named numbers.

Update the specification, implementation, and test suite.