LibAudio: Improve FLAC seeking

"Improve" is an understatement, since this commit makes all FLAC files
seek without errors, mostly with high accuracy, and partially even fast:
- A new generic seek table type is introduced, which keeps an
  always-sorted list of seek points, which allows it to use binary
  search and fast insertion.
- Automatic seek points are inserted according to two heuristics
  (distance between seek points and minimum seek precision), which not
  only builds a seek table for already-played sections of the file, but
  improves seek precision even for files with an existing seek table.
- Manual seeking by skipping frames works properly now and is still used
  as a last resort.

Userland/Libraries/LibAudio/CMakeLists.txt

@@ -1,4 +1,5 @@
 set(SOURCES
+    GenericTypes.cpp
     SampleFormats.cpp
     Loader.cpp
     WavLoader.cpp