LibAudio: Add a FLAC encoder

This encoder can handle all integer formats and sample rates, though
only two channels well. It uses fixed LPC and performs a
close-to-optimal parameter search on the LPC order and residual Rice
parameter, leading to decent compression already.

Meta/CMake/all_the_debug_macros.cmake

@@ -50,6 +50,7 @@ set(FAT_DEBUG ON)
 set(FILE_CONTENT_DEBUG ON)
 set(FILE_WATCHER_DEBUG ON)
 set(FILL_PATH_DEBUG ON)
+set(FLAC_ENCODER_DEBUG ON)
 set(FORK_DEBUG ON)
 set(FUTEX_DEBUG ON)
 set(FUTEXQUEUE_DEBUG ON)