preprocesser publicly exposes only preprocesser function

The preprocess_* functions are now privately contained within the
implementation file to help the preprocesser outer function.

Furthermore I've simplified the API of the preprocess_* functions by
making them only return pp_err_t and store their results in a vector
parameter taken by reference.

asm/preprocesser.hpp

@@ -44,14 +44,4 @@ std::ostream &operator<<(std::ostream &, pp_err_t &);
 
 pp_err_t preprocesser(const std::vector<token_t *> &, std::vector<token_t *> &);
 
-std::pair<std::vector<token_t *>, pp_err_t>
-preprocess_const_blocks(const std::vector<token_t *> &);
-
-std::pair<std::vector<token_t *>, pp_err_t>
-preprocess_use_blocks(const std::vector<token_t *> &);
-
-// TODO: Implement this
-std::pair<std::vector<token_t *>, pp_err_t>
-preprocess_macro_blocks(const std::vector<token_t *> &);
-
 #endif