Made use of libfuzzer

tests/fuzzers/http_header_parse.cpp

@@ -0,0 +1,9 @@
+#include "utility.hpp"
+#include <sstream>
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+  std::stringstream ss;
+  ss << std::string(reinterpret_cast<const char *>(data), size);
+  SimpleWeb::HttpHeader::parse(ss);
+  return 0;
+}