Added LEXBIN format to handle QZSS LEX raw frame

Added STRFMT_LEXBIN and lexbin.c to handle the QZSS LEX raw frame (for
SDR and LEX binary log).
LEX raw frame is 250 bytes (2000bits) including preamble, PRN, ID,
Alert, and RS code.
This added code only supports MADOCA-LEX (ID=12) because other LEX
doesn't contain time information in LEX raw frame...

rtkpost.exe, rtknavi.exe and rtkconv.exe are rebuiled and support LEXBIN
format.