Clean up error definitions, location and expose them in the headers

- Exposes all errors in the header file so any user of the api can test
   for the specific error conditions
 - Mark all static error pointers as const
 - Move generic errors into error.h
 - Name all errors err_modulename_* for errors that belong to a specific
   module and err_* for generic errors.

src/parser/util.h

@@ -21,6 +21,6 @@ parse_result_t parse_token(tokenlist_entry_t *current,
                            token_validator_t is_valid);
 parse_result_t parse_result_wrap(node_id_t id, parse_result_t result);
 
-extern error_t *err_parse_no_match;
+extern error_t *const err_parse_no_match;
 
 #endif // INCLUDE_PARSER_UTIL_H_