Sentry

- Avoid crash with invalid crashpad handler path.

- Send sessions to the correct sentry endpoint and make sure they work.
- Smaller cleanups.

- Avoid unsafe reads in the linux module finder.
- Update to latest crashpad snapshot.
- Yet more CMake improvements (thanks madebr and Amphaal).

Important upgrade notice

All `0.2.x` versions prior to this one were affected by a bug that could
potentially lead to serious data-loss on Windows platforms. We encourage
everyone to update as quickly as possible.
See [220](https://github.com/getsentry/sentry-native/issues/220) for details.

Deprecations

- `sentry_transport_t` will be replaced by an opaque struct with setter methods
in a future release.
- `sentry_backend_free` and `sentry_backend_t` are deprecated and will be
removed in a future release.

Other changes

- Further improvements to the cmake build system (huge thanks to madebr
[207](https://github.com/getsentry/sentry-native/pull/207))
- Improved support for older Windows versions, as low as Windows XP SP3 (thanks
to Mixaill [203](https://github.com/getsentry/sentry-native/pull/203),
cammm [202](https://github.com/getsentry/sentry-native/pull/202) and
jblazquez [212](https://github.com/getsentry/sentry-native/pull/212))
- Improved documentation
- Cleaned up sentry database handling
- Added new `sentry_handle_exception` function to explicitly capture a crash
(thanks cammm [201](https://github.com/getsentry/sentry-native/pull/201))
- Added new `sentry_clear_modulecache` function to clear the list of loaded
modules. Use this function when dynamically loading libraries at runtime.

- Implement experimental Session handling
- Implement more fine grained Rate Limiting for HTTP requests
- Implement `sample_rate` option
- In-process and Breakpad backend will not lose events queued for HTTP
submission on crash
- `sentry_shutdown` will better clean up after itself
- Add Experimental MinGW build support (thanks Amphaal
[189](https://github.com/getsentry/sentry-native/pull/189))
- Various other fixes and improvements

- fix: Run `Contextify` integration on `Threads` as well