devel/caf: Upgrade to 0.17.4. Changes since 0.17.3:

• Accept numbers as keys in the config syntax
• Fix behavior of inline_all_enqueues in the testing DSL
• Make sure actors that receive stream input shut down properly
• Fix undesired function hiding in fused_downstream_manager
• Improve to_string output for caf::error
• Fix path recognition in the URI parser, e.g., file:/// is now valid
• Properly report errors to users while connecting two CAF nodes
• Simplify crosscompilation: remove build dependency on code generators
• Leave CXX settings to the (CMake) parent when building as subdirectory
• Build without documentation in subdirectory mode
• Allow parents to set OPENSSL_INCLUDE_DIR in subdirectory mode
• Add -pthread flag on UNIX when looking for libc++ support
• Add missing operator== for exit_msg
• Avoid producing unexpected log files

Reported by: portscout, pkg-fallout
Approved by: ler (mentor, implicit)