- fixed compilation on Linux

libraries/oplsynth/oplio.cpp:59:32: error: ‘memset’ was not declared in this scope
src/sound/mididevices/midi_cvars.cpp:43:31: error: expected initializer before ‘GetSystemDirectoryA’

libraries/oplsynth/oplio.cpp

@@ -26,6 +26,8 @@
 #include <math.h>
 #include <assert.h>
 #include <algorithm>
+#include <string.h>
+
 #include "genmidi.h"
 #include "oplio.h"
 #include "opl.h"

src/sound/mididevices/midi_cvars.cpp

@@ -39,8 +39,10 @@
 #include "cmdlib.h"
 #include "doomerrors.h"
 
+#ifdef _WIN32
 // do this without including windows.h for this one single prototype
 extern "C" unsigned __stdcall GetSystemDirectoryA(char* lpBuffer, unsigned uSize);
+#endif // _WIN32
 
 static void CheckRestart(int devtype)
 {