Detect DV Fast Data on a per-frame basis

This commit adds a maybeFixupVoiceFrame() function that is used by
both the RF and Net code to manage FEC regeneration and DTMF blanking
in voice frames.

The presence of Fast Data is discovered by reading the mini-header in
every second data frame.  If found, FEC regeneration and DTMF blanking
are disabled for the current and next voice frames.

An exception is voice frames that have a sync frame instead of a data
frame.  This commit always disables FEC regeneration and DTMF blanking
for these frames.  A later commit will add support for these frames by
setting aside the voice frame until the next data frame can be read.

This commit also includes a number of debugging statements that will
be removed in a later commit.

MMDVMHost.cpp

@@ -668,7 +668,7 @@ int CMMDVMHost::run()
 			m_ump->setCD(cd);
 		}
 
-		unsigned char data[220U];
+		unsigned char data[MODEM_DATA_LEN];
 		unsigned int len;
 		bool ret;