add: 'wiegand commands' - wiegand manipulation like encoding / decoding of credentials. From offical repo (@grauerfuchs)

Adapted and converted to fit this repo.

client/util.c

@@ -878,3 +878,20 @@ char *strmcopy(const char *buf) {
     }
     return str;
 }
+
+/**
+ * Converts a hex string to component "hi2", "hi" and "lo" 32-bit integers, one nibble
+ * at a time.
+ *
+ * Returns the number of nibbles (4 bits) entered.
+ */
+int hexstring_to_u96(uint32_t* hi2, uint32_t* hi, uint32_t* lo, const char* str) {
+    int n = 0, i = 0;
+
+    while (sscanf(&str[i++], "%1x", &n ) == 1) {
+        *hi2 = (*hi2 << 4) | (*hi >> 28);
+        *hi = (*hi << 4) | (*lo >> 28);
+        *lo = (*lo << 4) | (n & 0xf);
+    }
+    return i - 1;
+}