Expose PHP fatal errors from the WASM interpreter

[adamziel]

Right now, PHP syntax errors cause the WASM PHP to return an exit code 2, but it doesn't return any error message. Let's make it provide a regular error message such as Fatal error: Class 'MyClass' not found in ...

[adamziel]

Solved in a59ef18 by adding a php.ini with display_startup_errors = On