Merge branch 'Mario/qc_updates' into 'master'

QC Updates

Updates mainly aiding transpilation, but also nice to have if sticking with DarkPlaces

* `float` -> `int`/`bool`
    * Helps the transpiler immensely
* Scope visibility reduction
* Replaces `#define` with `const`
    * More readable transpiler output (constant names instead of inline values)
* Replaces `vector_[xyz]` with `vector.[xyz]` (but not `entity.vector_[xyz]` because of a compiler bug)
* Removes `-Wno-double-declaration`
    * Required for compilation of transpiled source
* Removes useless uses of `var`, `noref` and `local`
* Uses `#include` instead of `progs.src`
    * Will help qc_physics

Squashed preview: [7239bacff8b7fb9fe9541d6c6dc852e78b5049ac](https://gitlab.com/xonotic/xonotic-data.pk3dir/commit/7239bacff8b7fb9fe9541d6c6dc852e78b5049ac?force_show_diff=true)

See merge request !97