Fixing a mistake in the UnixTime CPPUNIT test class. It was previously trying to convert the beginning of time (4XXXBC) into unix time, which is not possible. This value was changed to a valid time so that converting to unix time from commontime could be tested.
Fixing a mistake in the UnixTime CPPUNIT test class. It was previously trying to convert the beginning of time (4XXXBC) into unix time, which is not possible. This value was changed to a valid time so that converting to unix time from commontime could be tested.

git-svn-id: 6625e4d6743179724b113c04fbf297d122273a36@1931 108fab2b-820f-0410-9f2c-e5cc2c41d7be

ianmartin/GPSTk,ianmartin/GPSTk,ianmartin/GPSTk,ianmartin/GPSTk,ianmartin/GPSTk,ianmartin/GPSTk