feat(26.01): add bundle wrapper directory with NSIS sources and vendor symlinks

7-Zip 26.01 (ip7z/7zip) never shipped NSIS plugin sources, so they live in
a separate bundle directory (versions/26.01-bundle/) that mirrors the layout
expected by the shared overlay makefile and by MSBuild.

Bundle contents:
- CPP/7zip/Bundles/Nsis7z/: NSIS plugin wrapper sources (nsis7z.cpp,
  pluginapi.cpp, api.h, resource.rc, StdAfx.h, …) and the Windows build
  project file (Nsis7z_vs2026.vcxproj, adapted from versions/26.00/).
  The vcxproj references the vendor submodule tree via relative paths
  (../../../../../26.01/…), keeping the submodule pristine.
- CPP/7zip/UI/NSIS/: NSIS UI adapter sources (Main.cpp, MainAr.cpp,
  NSISBreak.cpp, ExtractCallbackConsole.cpp, UserInputUtils2.cpp and
  corresponding headers), copied from versions/26.00/.
- CPP/7zip/LzmaDec_gcc.mak: forwarding stub; GNU make resolves relative
  `include` paths against the CWD, so when make runs from Bundles/Nsis7z
  the upstream Arc_gcc.mak's `include ../../LzmaDec_gcc.mak` lands here.
  The stub re-includes the real file via $(VENDOR_7ZIP).
- Symlinks (C, Asm, CPP/7zip/*, CPP/Common, CPP/Windows, …) pointing into
  the versions/26.01 submodule.  These are required because the vendor
  makefile uses CWD-relative source paths (../../../../C/…, ../../Common/…).
  tools/linux/setup_26_01_bundle_symlinks.py recreates them if needed.

versions/26.01-bundle/CPP/7zip/UI/NSIS/UserInputUtils2.cpp

@@ -0,0 +1,60 @@
+// UserInputUtils.cpp
+
+#include "StdAfx.h"
+
+#include "Common/StdInStream.h"
+#include "Common/StringConvert.h"
+
+#include "UserInputUtils2.h"
+
+static const char kYes = 'Y';
+static const char kNo = 'N';
+static const char kYesAll = 'A';
+static const char kNoAll = 'S';
+static const char kAutoRename = 'U';
+static const char kQuit = 'Q';
+
+static const char *kFirstQuestionMessage = "?\n";
+static const char *kHelpQuestionMessage =
+  "(Y)es / (N)o / (A)lways / (S)kip all / A(u)to rename / (Q)uit? ";
+
+// return true if pressed Quite;
+// in: anAll
+// out: anAll, anYes;
+
+NUserAnswerMode::EEnum ScanUserYesNoAllQuit2(CStdOutStream *outStream)
+{
+  (*outStream) << kFirstQuestionMessage;
+  for(;;)
+  {
+    (*outStream) << kHelpQuestionMessage;
+	AString scannedString;
+	g_StdIn.ScanAStringUntilNewLine(scannedString);
+    scannedString.Trim();
+    if(!scannedString.IsEmpty())
+      switch(::MyCharUpper(scannedString[0]))
+      {
+        case kYes:
+          return NUserAnswerMode::kYes;
+        case kNo:
+          return NUserAnswerMode::kNo;
+        case kYesAll:
+          return NUserAnswerMode::kYesAll;
+        case kNoAll:
+          return NUserAnswerMode::kNoAll;
+        case kAutoRename:
+          return NUserAnswerMode::kAutoRename;
+        case kQuit:
+          return NUserAnswerMode::kQuit;
+      }
+  }
+}
+
+UString GetPassword(CStdOutStream *outStream)
+{
+  (*outStream) << "\nEnter password:";
+  outStream->Flush();
+  AString oemPassword;
+  g_StdIn.ScanAStringUntilNewLine(oemPassword);
+  return MultiByteToUnicodeString(oemPassword, CP_OEMCP);
+}