as far as i could tell this cast is unneeded because [GDBStub::SetServerPort](https://github.com/citra-emu/citra/blob/master/src/core/gdbstub/gdbstub.cpp#L897) takes a u16 and [values.gdbstub_port](https://github.com/citra-emu/citra/blob/master/src/core/settings.h#L116) is already a u16

* Removes circular dependences (common should not depend on core)

* implement frame limiter

* fixes

Allows users to choose a single screen layout or a large screen layout.
Adds a configuration option to change the prominent screen.

This makes clang-format useful on those.

Also add a bunch of forgotten transitive includes, which otherwise
prevented compilation.

Uses QSettings on citra-qt, and inih on citra-cli.