Make AlwaysLogUnhandledExceptions=off and CallUserHandlerOnFatals=EnableHipHopSyntax

Summary: By turning these off by default, we should match Zend behavior better on fatals with custom error handlers.

Few examples:
```
set_error_handler(function () { echo 'hello'; });
invalid();
```
This should produce only a fatal error message without calling user handler.

```
set_error_handler(function () { echo 'hello'; });
echo $invalid;
```
This should call user handler without producing notice message.

```
set_exception_handler(function () { echo 'hello'; });
throw new Exception();
```
This should call user handler without producing fatal error message.

Relates to #3019 and #4055.
Closes https://github.com/facebook/hhvm/pull/4066

Reviewed By: @ptarjan

Differential Revision: D1640294

Signature: t1:1640294:1414638838:69aa654fbc4b805b3f1731d786a4e0ad338d29aa