* math functions and high pass filter
high pass filter uses doubles to avoid numerical errors
* determinant check
Also reverse order such that output comes first in the argument list
* removed function prototypes
using [libtap](https://github.com/zorgnax/libtap) to create a [TAP](http://testanything.org) (TestAnythingProtocol) producer.
You can also run the test (if already compiled) with prove:
```
prove --exec '' tests/math/test_pprz_math.run
```
Ewoud Smeur
kirkscheper
Felix Ruess