Feature/handle mediatek nmea

[nogakeren]

Hi, this PR allows the SNR field to be a float (happens in some of the mediatek chipsets).

[hraftery]

Note change 1 will be made obsolete by #90 .

[nogakeren]

@hraftery removed first change

[nogakeren]

@kosma hi, can you please review my PR?

[kosma]

I'm looking at the PR and I'm slightly confused,

    if (!minmea_scan(sentence, "tiii;iiiiiiiiiiiiiiii",
    if (!minmea_scan(sentence, "tiii;iiifiiifiiifiiif",

The i format accepts an int *, while f accepts struct minmea_float *. If you change the format specifiers, you also have to change the field types here:

struct minmea_sat_info {
    int nr;
    int elevation;
    int azimuth;
    int snr;
};

Otherwise you're overwriting one byte past the structure and causing memory corruption. I'm surprised the tests pass. :o

[nogakeren]

@kosma nice catch, pushed a fixed version.
Are you cool with this API break, or should I keep SNR as an int and scan into some temp variable?

[nogakeren]

@kosma - can you please CR this change?

[kosma]

@nogakeren

1. I'm okay with the API change, it will cause a compiler error, so the user will know it needs updating.
2. The example in README and in example.c needs to be updated for the API change.
3. We should test parsing a float SNR value, for example in test_minmea_parse_gsv2.

[nogakeren]

@kosma
2. done
3. added a new test - test_minmea_parse_gsv6