Add SSLServer::ssl_context()

• Add SSLServer::ssl_context()
• Performance improvement for multipart form data file upload
• Fix keep-alive problem
• Add CPPHTTPLIB_LISTEN_BACKLOG

Fix problem when stopping a server

Can't properly stop server when using huge max keep alives (#1121)

Added patch version in user agent string

v0.9.9

Release v0.9.9

Fixed several issues

Allow to specify server IP address (#1067)
Accept protobuf encoding for compression (#1096)
Disable C++ exception with CPPHTTPLIB_NO_EXCEPTIONS (#1100)

Support custom SSL ctx configuration for SSLServer

#1073

Add retry logic for SSL_write

#1070

Fix bugs and performance improvement

#1023
#1037
#1054

Fix "Issue 37742 in oss-fuzz: cpp-httplib:server_fuzzer: Timeout in server_fuzzer"

v0.9.4

Fix "Issue 37742 in oss-fuzz: cpp-httplib:server_fuzzer: Timeout in s…

Added '_Online' suffix to unit test cases accessing external servers

v0.9.3

Append '_Online' suffix to Unit test names that access external servers

Fix some problems

Fix IPv6 addresses in host header not escaped. #998
Fix ca_cert_path/ce_cert_store lose #1004
Fix gzip compression/decompression over 4 GiB data size #1002