Reduce code stink (#1818)

CRC32.cpp:
Make table initialization compile time

DSi_NAND.cpp:
Fix file close / unmount / disk close on error
~L427: Remove redundant calls, as they are immediately rendered useless by `rem` being overwritten

NDS.cpp / FreeBIOS.h:
Remove unneeded size values in header
Remove unneeded memset's as they are initialized anyway

sha1.c / sha1.h:
Fix useless warning

Wifi.cpp:
Remove unneeded includes

DSi.cpp:
Reduce ugly casts
Deduplicate code

qt_sdl/main.cpp:
silence clang switch statement warning

qt_sdl/main.h:
fix override warnings

dolphin/BitSet.h:
use msvc extensions only when appropriate, fix broken bit set count under _WIN32

src/frontend/qt_sdl/main.h

@@ -354,7 +354,7 @@ private slots:
     void onScreenEmphasisToggled();
 
 private:
-    void closeEvent(QCloseEvent* event);
+    virtual void closeEvent(QCloseEvent* event) override;
 
     QStringList currentROM;
     QStringList currentGBAROM;