port an emufile fix from fceux

desmume/src/emufile.h

@@ -138,9 +138,14 @@ public:
 		//we dont generate straight into the buffer because it will null terminate (one more byte than we want)
 		int amt = vsnprintf(0,0,format,argptr);
 		char* tempbuf = new char[amt+1];
+
+		va_end(argptr);
+		va_start(argptr, format);
 		vsprintf(tempbuf,format,argptr);
+		
         fwrite(tempbuf,amt);
 		delete[] tempbuf;
+		
         va_end(argptr);
 		return amt;
 	};