www/c-icap: update to 0.5.6

Changelog:

• Possible buffer overflow if an ipv6 address is used with TlsPort
• Possible buffer overflow while building memcached key
• Not correctly initialized array, can cause undefined behavior to c-icap-stretch utility
• Bug 116: The CI_CONNECTION_CONNECTED ci_connection_t flag is not set properly
• Bug 115: Fix incorrect prototype for ci_client_get_server_options_nonblocking
• c-icap may crash while parsing wrong formated ICAP request line
• Fix many issues reported by clang analyzer, which may result to c-icap crashes or malfunction
• Using port with memcached server hostname, may result to c-icap crash
• Bug fix: Numeric as group/user id in Group/User cfg parameter does not work
• Many other fixes

PR: 242794
Submitted by: Franco Fichtner <franco@opnsense.org>