Improve checking of used types in BuiltinFunctionEmbedder

BuiltinFunctionEmbedded creates the link between C++ and pugs.

Nothing forbids at compilation time to use types that have no correspondence in the language. For instance, one can use int arguments, but it will fail to create the mapping when loading the function. The correct types for integers are unit64_t or int64_t.

One must improve the class so that it detects at compile time (at least for basic types) invalid type usage since this kind of bugs can be a bit difficult to identify