Missing SatelliteSystem::Mixed enum value in systemChar(), systemString(), systemString3() functions

[Grawta]

Our test case:

• Read a Mixed satellite system Rinex V2.11 file, rewrite it, then open the new file. An exception occurs at the last step.

Issue

• If our file has a header with M (Mixed) value for satellite System , it will be read but when printing the header, in systemChar(), systemString(), systemString3() functions we are missing the M (Mixed) case which will lead to "? (Unknown)". When opening the new file, an exception will be raised saying that Unknown is not supported.

Proposed correction

• Add a case for SatelliteSystem::Mixed in systemChar(), systemString(), systemString3() functions in file RinexSatID.cpp.