mbedtls: fix building with <3.6.1

[vszakats]

lib/vtls/mbedtls.c:786:3: error: call to undeclared function 'mbedtls_ssl_conf_tls13_enable_signal_new_session_tickets'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
  786 |   mbedtls_ssl_conf_tls13_enable_signal_new_session_tickets(&backend->config,
      |   ^
lib/vtls/mbedtls.c:787:5: error: use of undeclared identifier 'MBEDTLS_SSL_TLS1_3_SIGNAL_NEW_SESSION_TICKETS_ENABLED'; did you mean 'MBEDTLS_SSL_TLS1_3_NEW_SESSION_TICKET_FLUSH'?
  787 |     MBEDTLS_SSL_TLS1_3_SIGNAL_NEW_SESSION_TICKETS_ENABLED);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |     MBEDTLS_SSL_TLS1_3_NEW_SESSION_TICKET_FLUSH
dep/mbedtls-3.4.0/_pkg/include/mbedtls/ssl.h:700:5: note: 'MBEDTLS_SSL_TLS1_3_NEW_SESSION_TICKET_FLUSH' declared here
  700 |     MBEDTLS_SSL_TLS1_3_NEW_SESSION_TICKET_FLUSH,
      |     ^
2 errors generated.

Regression from d63e40f #18271 (8.16.0)

[vszakats]

Unrelated, relatively non-flaky, fuzzer report in curl_fuzzer_ws:

==22== ERROR: libFuzzer: timeout after 27 seconds
    #0 0x555e2e179571 in __sanitizer_print_stack_trace /src/llvm-project/compiler-rt/lib/asan/asan_stack.cpp:87:3
    #1 0x555e2e06b318 in fuzzer::PrintStackTrace() /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerUtil.cpp:210:5
    #2 0x555e2e04dded in fuzzer::Fuzzer::AlarmCallback() /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:304:5
    #3 0x7fa17120341f  (/lib/x86_64-linux-gnu/libpthread.so.0+0x1441f) (BuildId: 5cfb896dd40f90aa8c6c8bb856004d1f5cfe293c)
    #4 0x7fa1712034f5 in __libc_sigaction (/lib/x86_64-linux-gnu/libpthread.so.0+0x144f5) (BuildId: 5cfb896dd40f90aa8c6c8bb856004d1f5cfe293c)
    #5 0x555e2e201bbc in sigpipe_restore /src/curl/lib/sigpipe.h:77:5
    #6 0x555e2e201bbc in curl_multi_perform /src/curl/lib/multi.c:2805:3
    #7 0x555e2e1b3008 in fuzz_handle_transfer(fuzz_data*) /src/curl_fuzzer/curl_fuzzer.cc:419:5
    #8 0x555e2e1b1fd7 in LLVMFuzzerTestOneInput /src/curl_fuzzer/curl_fuzzer.cc:97:3
    #9 0x555e2e04f54d in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:619:13
    #10 0x555e2e04eb85 in fuzzer::Fuzzer::RunOne(unsigned char const*, unsigned long, bool, fuzzer::InputInfo*, bool, bool*) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:516:7
    #11 0x555e2e050ec2 in fuzzer::Fuzzer::ReadAndExecuteSeedCorpora(std::__Fuzzer::vector<fuzzer::SizedFile, std::__Fuzzer::allocator<fuzzer::SizedFile>>&) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:834:7
    #12 0x555e2e0511c8 in fuzzer::Fuzzer::Loop(std::__Fuzzer::vector<fuzzer::SizedFile, std::__Fuzzer::allocator<fuzzer::SizedFile>>&) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:872:3
    #13 0x555e2e040055 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:917:6
    #14 0x555e2e06bcc2 in main /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerMain.cpp:20:10
    #15 0x7fa170e89082 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24082) (BuildId: 0323ab4806bee6f846d9ad4bccfc29afdca49a58)
    #16 0x555e2e0333ad in _start (build-out/curl_fuzzer_ws+0x66b3ad)

DEDUP_TOKEN: __sanitizer_print_stack_trace--fuzzer::PrintStackTrace()--fuzzer::Fuzzer::AlarmCallback()
SUMMARY: libFuzzer: timeout

https://github.com/curl/curl/actions/runs/18764330306/job/53537738646?pr=19208