mdbx-windows: fix mdbx_RegGetValue() for Windows 2000/XP.

Change-Id: I436a254300fcba8dbf75ea7568c2bf0c963fe060

src/osal.h

@@ -887,6 +887,12 @@ static __inline bool mdbx_RunningUnderWine(void) {
   return !mdbx_NtExtendSection;
 }
 
+typedef LSTATUS(WINAPI *MDBX_RegGetValueA)(HKEY hkey, LPCSTR lpSubKey,
+                                           LPCSTR lpValue, DWORD dwFlags,
+                                           LPDWORD pdwType, PVOID pvData,
+                                           LPDWORD pcbData);
+MDBX_INTERNAL_VAR MDBX_RegGetValueA mdbx_RegGetValueA;
+
 #endif /* Windows */
 
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