fix: compilation error because of multiple function declarations

```/home/poz/local/include/yara/re.h:178:10: error: redundant redeclaration of ‘yr_re_node_create’ [-Werror=redundant-decls]
 RE_NODE* yr_re_node_create(
          ^
/home/poz/local/include/yara/re.h:164:10: note: previous declaration of ‘yr_re_node_create’ was here
 RE_NODE* yr_re_node_create(
          ^
cc1: all warnings being treated as errors
```