Sentry-php: Adding stack traces via captureEvent

[TamasSzigeti]

Hi,

seems Sentry\Client#captureEvent doesn't apply the attach_stacktrace option as captureMessage does, and there seems to be no easy way to send stack traces along with events, unless it is an exception.

Can this tiny but important feature be added, please?

[Jean85]

This seems more of a bug than a feature IMHO; thanks for reporting this.

@HazAT @ste93cry @stayallive do you agree?

[ste93cry]

It's a bug indeed, thus I created a PR to fix it