Updates to built-in types interface, fixes to problematic dependencies, and improved matching in peval

[br4sco]

This PR:

• Changes the interface of the default symbolize and type-check environments so that it is easier to extend the built-in types. A change that might affect other projects using the miking compiler is that symEnvEmpty is now called symEnvDefault to reflect that the default environment contains the built-in types in MExpr. Similarly, _tcEnvEmpty is renamed to typcheckEnvDefault to also indicate that it is public. Fore each environment there is a empty version that is truly empty and there is a function {sym,typcheck}EnvAddBuiltinTypes to more conveniently add builtin types to the environments.
• Removes an unused include in keyword-maker.mc that broke the the lexer when including both parser/lexer.mc and keyword-maker.mc. It is typically a bad idea to duplicate the names of language fragments with different implementations as is the case for parser/lexer.mc and mexpr/parser.mc when the include order is hard to control/foresee.
• Improves matching in peval.mc and fixes a possible bug with incorrect name capturing.