Assert: Uppercase assertion macros

Macros should be all upper-cased. This is also kind of a wart that's
been sticking out for quite a while now (we avoid prefixing
underscores).

Source/Core/Common/SysConf.h

@@ -55,7 +55,7 @@ public:
     template <typename T>
     void SetData(T value)
     {
-      _assert_(sizeof(value) == bytes.size());
+      ASSERT(sizeof(value) == bytes.size());
       std::memcpy(bytes.data(), &value, bytes.size());
     }