Why not using abs() from stdlib?

Why does Arduino.h use its own abs() if stdlib has this already builtin. This causes me problems in build environments. I dont see any reason why one would prefer an Arduino definition. Can we get rid of it?
```
#define abs(x) ((x)>0?(x):-(x))
```

Start by reading Arduino.h and locating the local abs(x) macro shown in the issue. Check how the standard library and affected build environments resolve abs, then verify that removing the Arduino definition does not break existing Arduino API builds or users that rely on it.

Written by the indexing model from the issue text.