refactor: initial migration to QuaZip 1.2

Let's move off our custom QuaZip. In the olden times we needed the
custom version of QuaZip, as it was basically unmaintained and on
SourceForge (eww). But nowadays it's maintained and on GitHub. See
new GitHub page: https://github.com/stachenov/quazip

launcher/MMCZip.h

@@ -21,17 +21,21 @@
 #include "minecraft/mod/Mod.h"
 #include <functional>
 
-#include <JlCompress.h>
+//#include <QuaZip-Qt5-1.2/quazip/JlCompress.h>
+// TODO: Blocked by https://github.com/stachenov/quazip/pull/141
+// For now, checkout https://github.com/Scrumplex/quazip/tree/expose-jlcompress-fns at ../../quazip
+#include <../../quazip/quazip/JlCompress.h>
 #include <nonstd/optional>
 
 namespace MMCZip
 {
+    using FilterFunction = std::function<bool(const QString &)>;
 
     /**
      * Merge two zip files, using a filter function
      */
     bool mergeZipFiles(QuaZip *into, QFileInfo from, QSet<QString> &contained,
-                                            const JlCompress::FilterFunction filter = nullptr);
+                                            const FilterFunction filter = nullptr);
 
     /**
      * take a source jar, add mods to it, resulting in target jar