PHP incompatibility with multiple error handlers

HHVM behaves differently than PHP when multiple error handlers interact with each other. In PHP, you can call `restore_error_handler()` followed by `trigger_error()` inside an error handler to essentially pass the error on to the next error handler. In HHVM, this doesn't happen.
### HHVM Version

```
HipHop VM 3.12.1 (rel)
Compiler: tags/HHVM-3.12.1-0-gf516f1bb9046218f89885a220354c19dda6d8f4d
Repo schema: f2e5f39b2ad4a08bcbd90b5d8bcb580f40fba6c8
```
### Standalone code, or other way to reproduce the problem

https://3v4l.org/kA5pA

```