Add xReallocArrayZero() helper

Add helper function to reallocate an dynamic allocated array including
zeroing the newly allocated memory.

XUtils.c

@@ -78,6 +78,22 @@ void* xReallocArray(void* ptr, size_t nmemb, size_t size) {
    return xRealloc(ptr, nmemb * size);
 }
 
+void* xReallocArrayZero(void* ptr, size_t prevmemb, size_t newmemb, size_t size) {
+   assert((ptr == NULL) == (prevmemb == 0));
+
+   if (prevmemb == newmemb) {
+      return ptr;
+   }
+
+   void* ret = xReallocArray(ptr, newmemb, size);
+
+   if (newmemb > prevmemb) {
+      memset((unsigned char*)ret + prevmemb * size, '\0', (newmemb - prevmemb) * size);
+   }
+
+   return ret;
+}
+
 inline bool String_contains_i(const char* s1, const char* s2) {
    return strcasestr(s1, s2) != NULL;
 }

XUtils.h

@@ -30,6 +30,8 @@ void* xRealloc(void* ptr, size_t size) ATTR_ALLOC_SIZE1(2);
 
 void* xReallocArray(void* ptr, size_t nmemb, size_t size) ATTR_ALLOC_SIZE2(2, 3);
 
+void* xReallocArrayZero(void* ptr, size_t prevmemb, size_t newmemb, size_t size) ATTR_ALLOC_SIZE2(3, 4);
+
 /*
  * String_startsWith gives better performance if strlen(match) can be computed
  * at compile time (e.g. when they are immutable string literals). :)