Raylib source code assert() replacement macro does not work

The hack of trying to replace all asserts with a global macro to something that R will handle does not work.

The following R code will crash, instead of throwing an error:

```R
library(raylib.R)
init_window(-1,-1,"")
```

Expecting R to handle the error. Possible solution is to use a macro per file, instead of a global -D option macro.