* Added an 'RDAudioConvert::Stage3Pcm24()' method in
'lib/rdaudioconvert.cpp' and 'lib/rdaudioconvert.h'.
* Added a 'Format::Pcm24' value to the 'RDSettings::Format'
enumeration in 'lib/rdsettings.h'.
* Modified the 'RDAudioConvert' class to support generating PCM24
output in 'lib/rdaudioconvert.cpp' and 'lib/rdaudioconvert.h'.
* Modified the 'RDPlayStream' class to support playing PCM24
data in 'rdhpi/rdplaystream.cpp'.
* Modified the 'RDRecordStream' class to support capturing PCM24
data in 'rdhpi/rdrecordstream.cpp'.
* Added an 'audio_peaks_test' harness in 'tests/audio_peaks_test.cpp'
and 'tests/audio_peaks_test.h'.
* Added 'PCM24' to the list of available formats in
'rdadmin/edit_rdlibrary.cpp' and 'rdadmin/edit_rdlibrary.h'.
* Added 'PCM24' to the list of available formats in
'rdadmin/edit_decks.cpp'.
* Added PCM24 support for file importation in
'web/rdxport/import.cpp'.
* Added an 'RDCae::Pcm24' value to the 'RDCae::AudioCoding
enumeration in 'lib/rdcae.h'.
