sauwming

As reported in #3203, `upnpdebug.h` may not be available in the installation location if `libupnp` is not build with `--enable-debug`, so we shouldn't include it by default.

The change in the latest PR #3166 causes a build failure on Mac since `is_running` variable declaration is within the macro `TARGET_OS_IPHONE`.

Add OpenSSL version check for SSL_SESSION_is_resumable()

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The function is only available in OpenSSL 1.1.1 (instead of 1.1.0). https://www.openssl.org/docs/man1.1.1/man3/SSL_SESSION_is_resumable.html Thanks to @formater for the info.

Currently `pjmedia_transport_srtp_stop()` will deallocate the SRTP contexts but doesn't reset them to NULL. This can potentially cause crash in `pjmedia_transport_get_info()` which will call `srtp_get_stream_roc()` to the contexts. ``` #00 pc...

The Subscription-State header field in a NOTIFY request can contain parameters, such as "expires" and "reason". ``` Subscription-State = "Subscription-State" HCOLON substate-value *( SEMI subexp-params ) substate-value = "active" /...

To fix #2930. It is reported that initiating SSL connection can trigger an assertion: `Assertion failed: (ssock->send_buf.max_len == 0), function ssock_on_connect_complete, file ../src/pj/ssl_sock_imp_common.c, line 1134.` Upon investigation, it turns out...