Restore removed <algorithm> includes.

Turns out these were needed after all. For some reason, on Windows and
Mac, <algorithm> gets auto-included by something else so I don't notice
when it's missing, and MSVC's include dependency tracker doesn't see it
either.

GPU/Common/VertexDecoderCommon.cpp

@@ -17,6 +17,10 @@
 
 #include "ppsspp_config.h"
 
+#include <algorithm>
+#include <vector>
+#include <string>
+
 #include "Common/CommonTypes.h"
 #include "Common/Data/Convert/ColorConv.h"
 #include "Common/Log.h"