Fix some errors found by fuzzers (#2078)

Fix compilation on Windows.
"dirent.h" file has been taken from https://github.com/tronkko/dirent/

Fix Python bindings

Fix some warnings with x86_64-w64-mingw32-gcc:
```
protocols/dns.c: In function ‘ndpi_search_dns’:
protocols/dns.c:775:41: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
  775 |       unsigned long first_element_len = (unsigned long)dot - (unsigned long)_hostname;
      |                                         ^
protocols/dns.c:775:62: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
  775 |       unsigned long first_element_len = (unsigned long)dot - (unsigned long)_hostname;
      |
```
```
In file included from ndpi_bitmap64.c:31:
third_party/include/binaryfusefilter.h: In function ‘binary_fuse8_hash’:
third_party/include/binaryfusefilter.h:160:32: error: left shift count >= width of type [-Werror=shift-count-overflow]
  160 |     uint64_t hh = hash & ((1UL << 36) - 1);
```
```
In function ‘ndpi_match_custom_category’,
    inlined from ‘ndpi_fill_protocol_category.part.0’ at ndpi_main.c:7056:16:
ndpi_main.c:3419:3: error: ‘strncpy’ specified bound depends on the length of the source argument [-Werror=stringop-overflow=]
 3419 |   strncpy(buf, name, name_len);
```

1 files changed, 14 insertions, 2 deletions

diff --git a/src/lib/ndpi_main.c b/src/lib/ndpi_main.c
index ae3c4c200..c2a5b2f2f 100644
--- a/src/lib/ndpi_main.c
+++ b/src/lib/ndpi_main.c
@@ -2669,7 +2669,8 @@ void ndpi_debug_printf(unsigned int proto, struct ndpi_detection_module_struct *
 
 void set_ndpi_debug_function(struct ndpi_detection_module_struct *ndpi_str, ndpi_debug_function_ptr ndpi_debug_printf) {
 #ifdef NDPI_ENABLE_DEBUG_MESSAGES
-  ndpi_str->ndpi_debug_printf = ndpi_debug_printf;
+  if(ndpi_str)
+    ndpi_str->ndpi_debug_printf = ndpi_debug_printf;
 #endif
 }
 
@@ -3002,7 +3003,15 @@ struct ndpi_detection_module_struct *ndpi_init_detection_module(ndpi_init_prefs
     ac_automata_name(ndpi_str->custom_categories.hostnames_shadow.ac_automa, "ccat_sh", 0);
 #else
   ndpi_str->custom_categories.sc_hostnames        = ndpi_domain_classify_alloc();
+  if(!ndpi_str->custom_categories.sc_hostnames) {
+    ndpi_exit_detection_module(ndpi_str);
+    return(NULL);
+  }
   ndpi_str->custom_categories.sc_hostnames_shadow = ndpi_domain_classify_alloc();
+  if(!ndpi_str->custom_categories.sc_hostnames_shadow) {
+    ndpi_exit_detection_module(ndpi_str);
+    return(NULL);
+  }
 #endif
 
   ndpi_str->custom_categories.ipAddresses = ndpi_patricia_new(32 /* IPv4 */);
@@ -3407,7 +3416,7 @@ int ndpi_match_custom_category(struct ndpi_detection_module_struct *ndpi_str,
   u_int max_len = sizeof(buf)-1;
     
   if(name_len > max_len) name_len = max_len;
-  strncpy(buf, name, name_len);
+  memcpy(buf, name, name_len);
   buf[name_len] = '\0';
   
   if(ndpi_domain_classify_contains(ndpi_str->custom_categories.sc_hostnames,
@@ -6887,6 +6896,9 @@ int ndpi_load_hostname_category(struct ndpi_detection_module_struct *ndpi_str,
 			       (AC_AUTOMATA_t *)ndpi_str->custom_categories.hostnames_shadow.ac_automa,
 			       name_to_add,category,category, 0, 0, 1); /* at_end */
 #else
+  if(ndpi_str->custom_categories.sc_hostnames_shadow == NULL)
+    return(-1);
+
   return(ndpi_domain_classify_add(ndpi_str->custom_categories.sc_hostnames_shadow,
 				  (u_int16_t)category, (char*)name_to_add) ? 0 : -1);
 #endif