[BUG] Receiving SIGINT while inside a napms() call leads to crash

**Describe the bug**

When using one of the `s4c_animate_` functions, if an interrupt handler is installed by the program and `SIGINT` is received, the program will crash because `napms()` is not interrupt-handler-safe.

- Version: `>=0.1.5`

**Additional context**

This [link](https://www.qnx.com/developers/docs/7.0.0/index.html#com.qnx.doc.neutrino.lib_ref/topic/n/napms.html) mentions the fact that `napms()` is not safe with interrupt handlers.