Implement primitive console output

[y5nw]

• The function for commands should have the same prototype as regular C functions, i.e. they take the number of arguments and the list of arguments - using this instead of varargs allows the command name to be passed as argv[0], like in C. Note that, unlike C, argc represents the number of arguments excluding argv[0]. This makes argc effectively a shorthand for #argv.
• Console output works like in Lua, i.e. via the io library and the print function. However, only a subset of the io library (specifically, the part that is relevant to printing to stdout) is implemented.

Note: #6 is needed before some minor issues can be addressed.

[JamesClarke7283]

Are you ready for review?