add ota algorithm for device

1. effective "Differential Upgrade" patch algorithm with high compression rate
2. effective recovery algorithm support recovery firmware in blocks which has low memory consumption and wear-leveling strategies, especially suitable for embeded devices with low RAM.
3. add sample ota bootloader project, see:
board\TencentOS_tiny_EVB_MX_Plus\KEIL\ota\ota_bootloader_recovery
4. add sample application project for download firmware through http, see:
board\TencentOS_tiny_EVB_MX_Plus\KEIL\ota\ota_application_download_through_http
5. add sample application project for download firmware through qcloud explorer console, see:
board\TencentOS_tiny_EVB_MX_Plus\KEIL\ota\ota_application_download_through_qcloud_iot_explorer
6. an OTA markdown document is pending

components/ota/common/lzma/3rdparty/DllSecur.c

@@ -0,0 +1,108 @@
+/* DllSecur.c -- DLL loading security
+2018-02-21 : Igor Pavlov : Public domain */
+
+#include "Precomp.h"
+
+#ifdef _WIN32
+
+#include <windows.h>
+
+#include "DllSecur.h"
+
+#ifndef UNDER_CE
+
+typedef BOOL (WINAPI *Func_SetDefaultDllDirectories)(DWORD DirectoryFlags);
+
+#define MY_LOAD_LIBRARY_SEARCH_USER_DIRS 0x400
+#define MY_LOAD_LIBRARY_SEARCH_SYSTEM32  0x800
+
+static const char * const g_Dlls =
+  #ifndef _CONSOLE
+  "UXTHEME\0"
+  #endif
+  "USERENV\0"
+  "SETUPAPI\0"
+  "APPHELP\0"
+  "PROPSYS\0"
+  "DWMAPI\0"
+  "CRYPTBASE\0"
+  "OLEACC\0"
+  "CLBCATQ\0"
+  "VERSION\0"
+  ;
+
+#endif
+
+void My_SetDefaultDllDirectories()
+{
+  #ifndef UNDER_CE
+  
+    OSVERSIONINFO vi;
+    vi.dwOSVersionInfoSize = sizeof(vi);
+    GetVersionEx(&vi);
+    if (!GetVersionEx(&vi) || vi.dwMajorVersion != 6 || vi.dwMinorVersion != 0)
+    {
+      Func_SetDefaultDllDirectories setDllDirs = (Func_SetDefaultDllDirectories)
+          GetProcAddress(GetModuleHandle(TEXT("kernel32.dll")), "SetDefaultDllDirectories");
+      if (setDllDirs)
+        if (setDllDirs(MY_LOAD_LIBRARY_SEARCH_SYSTEM32 | MY_LOAD_LIBRARY_SEARCH_USER_DIRS))
+          return;
+    }
+
+  #endif
+}
+
+
+void LoadSecurityDlls()
+{
+  #ifndef UNDER_CE
+  
+  wchar_t buf[MAX_PATH + 100];
+
+  {
+    // at Vista (ver 6.0) : CoCreateInstance(CLSID_ShellLink, ...) doesn't work after SetDefaultDllDirectories() : Check it ???
+    OSVERSIONINFO vi;
+    vi.dwOSVersionInfoSize = sizeof(vi);
+    if (!GetVersionEx(&vi) || vi.dwMajorVersion != 6 || vi.dwMinorVersion != 0)
+    {
+      Func_SetDefaultDllDirectories setDllDirs = (Func_SetDefaultDllDirectories)
+          GetProcAddress(GetModuleHandle(TEXT("kernel32.dll")), "SetDefaultDllDirectories");
+      if (setDllDirs)
+        if (setDllDirs(MY_LOAD_LIBRARY_SEARCH_SYSTEM32 | MY_LOAD_LIBRARY_SEARCH_USER_DIRS))
+          return;
+    }
+  }
+
+  {
+    unsigned len = GetSystemDirectoryW(buf, MAX_PATH + 2);
+    if (len == 0 || len > MAX_PATH)
+      return;
+  }
+  {
+    const char *dll;
+    unsigned pos = (unsigned)lstrlenW(buf);
+
+    if (buf[pos - 1] != '\\')
+      buf[pos++] = '\\';
+    
+    for (dll = g_Dlls; dll[0] != 0;)
+    {
+      unsigned k = 0;
+      for (;;)
+      {
+        char c = *dll++;
+        buf[pos + k] = (Byte)c;
+        k++;
+        if (c == 0)
+          break;
+      }
+
+      lstrcatW(buf, L".dll");
+      LoadLibraryExW(buf, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
+    }
+  }
+  
+  #endif
+}
+
+#endif