Operating system counter stores signals as flag set without counter.
So sending two signals to a process may result to one or two signal
handler invocation. Queueing signals inside Idris could give users
false sense of signals being are queue, while they are not.
In particular, test for signal could not work reliably for that
reason.
Also, practically we usually don't need have more than once signal
event.
This is follow-up to #1660. CC @mattpolzin
```
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.
Support for simple signal handling was added in
a0a417240e. This commit also adds the
`_simple_handler` function. It seems to me that this function is
intended as a helper function which should only be visible in
`idris_signal.c`, it is not used outside this file. For this purpose it
is probably also marked as inline. However, the inline keyword does not
require the compiler to actually inline the function. As such, the
`_simple_handler` symbol may still be exported if the compiler doesn't
inline the function.
On my system this seems to be the case and causes the following error
during compilation of idris2:
Exception: (while loading libidris2_support.so) Error relocating Idris2-0.4.0/build/exec/idris2_app/libidris2_support.so: _simple_handler: symbol not found
By marking the `_simple_handler` function as `static inline` it is
ensured that the symbol is not exported, thereby preventing the
relocation error.
