* Add function that checks whether a file is a terminal device.
* support isTTY function for NodeJS backend.
* don't accidentally interpret 'false' string as truthy number
* less code duplication.
```
IDRIS2_VERIFY(cond, message_format, ...)
```
When condition is false, crash.
Used in native functions where correct error handling is hard or
not impossible.
For example, `malloc` rarely fails, but if it fails, better crash
with clear error message than spend time debugging null pointer
dereference.
It seems relevant to all BSD systems.
In xcode the option -Wno-error-implicit-function-declaration is enabled. So the following error occured:
Idris2/support/c/idris_file.c:76:13: Missing '#include <sys/time.h>'; declaration of 'select' must be imported from module 'Darwin.POSIX.sys.time' before it is required
I hope it won't break anything on linux.
