[client] usbredir: add parser bridge

Add a serialized bridge between PureSpice USB redirection channels and
libusbredirparser.

Claim one channel and stream borrowed fragments directly through the
parser without packet allocations. Provide an atomic device plug request
for later audio integration.

client/CMakeLists.txt

@@ -79,6 +79,25 @@ if(ENABLE_AUDIO AND NOT (ENABLE_PIPEWIRE OR ENABLE_PULSEAUDIO))
 endif()
 add_feature_info(ENABLE_AUDIO ENABLE_AUDIO "Audio support.")
 
+cmake_dependent_option(
+  ENABLE_USB_AUDIO
+  "Build with USB audio support"
+  ON
+  "ENABLE_AUDIO"
+  OFF
+)
+
+if(ENABLE_USB_AUDIO)
+  pkg_check_modules(USBREDIRPARSER QUIET IMPORTED_TARGET
+    libusbredirparser-0.5>=0.7.1)
+  if(NOT USBREDIRPARSER_FOUND)
+    message(STATUS
+      "libusbredirparser was not found, disabling USB audio support")
+    set(ENABLE_USB_AUDIO OFF)
+  endif()
+endif()
+add_feature_info(ENABLE_USB_AUDIO ENABLE_USB_AUDIO "USB audio support.")
+
 add_compile_options(
   "-Wall"
   "-Wextra"
@@ -195,6 +214,12 @@ if(ENABLE_AUDIO)
   )
 endif()
 
+if(ENABLE_USB_AUDIO)
+  list(APPEND SOURCES
+    src/usbredir.c
+  )
+endif()
+
 add_subdirectory("${PROJECT_TOP}/resources"       "${CMAKE_BINARY_DIR}/resources")
 add_subdirectory("${PROJECT_TOP}/common"          "${CMAKE_BINARY_DIR}/common"   )
 add_subdirectory("${PROJECT_TOP}/repos/LGMP/lgmp" "${CMAKE_BINARY_DIR}/LGMP"     )
@@ -259,6 +284,13 @@ if(ENABLE_AUDIO)
   )
 endif()
 
+if(ENABLE_USB_AUDIO)
+  target_compile_definitions(looking-glass-client PRIVATE ENABLE_USB_AUDIO)
+  target_link_libraries(looking-glass-client
+    PkgConfig::USBREDIRPARSER
+  )
+endif()
+
 install(TARGETS looking-glass-client
   RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
   COMPONENT binary)