From John Hay:
authorrobertl <robertl>
Wed, 25 Aug 2004 13:12:08 +0000 (13:12 +0000)
committerrobertl <robertl>
Wed, 25 Aug 2004 13:12:08 +0000 (13:12 +0000)
commit659f918c754a1a60d1783c9ee8dcee9ca18c7c15
treea1784de596e36969dbf15669b38d7c764fa54400
parent87f82bbb449b32a9711cf94742c6b02bf20d5256
From John Hay:
  added code to verify the checksum and discard the line if it doesn't match
  discard the line if the position fix wasn't valid.
  extract date from gprmc if available.
nmea.c