One build 270 crash log aborts in talloc (talloc_abort_unknown_value)
inside libsmbclient name resolution while a media-source download opens
a file through SMBBridge, with FFmpeg reading an smb:// file on another
thread at the same time.
libsmbclient keeps its talloc stackframe behind a table of thread
functions, and none was installed (this build does not export
smbc_thread_posix()), so every thread shared one stackframe and the two
users freed each other's allocations. Install a pthread implementation
of smb_thread_functions at load time, before any libsmbclient use,
including FFmpeg's. The struct layout matches what talloc_stack and
smb_threads in the bundled library read (get_tls at +0x30, lock_mutex
at +0x10).
Delete declarations that Periphery reports unused on every platform that
compiles them (iOS, macOS, tvOS), including nine views used only by their
own previews. Platform-gated code still used on another platform, device-
only MPV render paths, migration models, CloudKit record names, App
Intents metadata and unused parameters are kept.
