Adds RemoveNulls trasnformation

src/utils.cc

@@ -809,5 +809,20 @@ static unsigned char x2c(unsigned char *what) {
 }
 
 
+std::string string_to_hex(const std::string& input) {
+    static const char* const lut = "0123456789ABCDEF";
+    size_t len = input.length();
+
+    std::string output;
+    output.reserve(2 * len);
+    for (size_t i = 0; i < len; ++i) {
+        const unsigned char c = input[i];
+        output.push_back(lut[c >> 4]);
+        output.push_back(lut[c & 15]);
+    }
+    return output;
+}
+
+
 }  // namespace ModSecurity