Issue #276 - conversion functions between std::wstring and ATL::CString

src/plugin/ATL_Deprecate.h

 /**
  * \file ATL_Deprecate.h Include package for all the ATL headers, with optional forwarding to detect ATL dependencies.
  *
  * This header is a nexus for refactoring work to remove ATL.
  * The main purpose of this mechanism is to determine the exact scope of the refactoring effort.
  * The lifetime of this header is during the work on #276 Stop using ATL https://issues.adblockplus.org/ticket/276
  *
  * This file implements namespace forwarding that allows detection of ATL symbols.
  * This forwarding is ordinarily disabled, and always disabled in Release configuration for safety.
  * When forwarding is disabled, it simply includes the ATL headers.
@@ skipping 110 matching lines @@
 #endif
 
 /*
  * Deprecation pragmas use the compiler to identify refactoring targets.
  */
 #if DISABLE_ATL_FORWARDING
 namespace ATL {
 #else 
 namespace OLD_ATL {
 #endif
+#pragma deprecated( CComBSTR )
 #pragma deprecated( CRect )
 #pragma deprecated( CSimpleArray )
 }
 
 /*
  * Note:
  *   The preprocessor symbols ATLASSERT and ATLTRACE appear in the source.
  *   These resolve to nothing in Release configurations.
  *   In Debug configurations, these are non-trivial.
  *   ATLASSERT resolves to an expression with _CrtDbgReportW and _CrtDbgBreak.
  *   ATLTRACE resolves to a ATL::CTraceFileAndLineInfo.
  *   These will need to be replaced or removed.
  */
+
+
+/*
+ * Transient functions used during the ATL removal process.
+ *
+ * Trying to convert all the string instances at once leads to massive change sets.
+ * In order to be able to convert incrementally, we'll need to undergo a period where we're mixing types.
+ * The functions below are explicit conversion functions.
+ * While it's possible to convert them by direct calls to member functions,
+ *   using explicit conversion functions will allow us to ensure we've removed all the conversions when we're done.
+ *
+ * These are declared in ATL_Deprecate.h to ensure that they're all removed before we ATL removal is complete.
+ *
+ * Reference:
+ *   MSDN CString http://msdn.microsoft.com/en-us/library/aa300688%28v=vs.60%29.aspx
+ */
+
+#include <string>
+/**
+ * Conversion function from ATL:CString to std::wstring
+ *
+ * The argument cannot be declared 'const' because of the CString API.
+ * Reference argument usually does not require explicit temporaries.
+ */
+std::wstring to_wstring(const ATL::CString& s);
+
+/**
+ * Conversion function from std::wstring to ATL::CString
+ */
+ATL::CString to_CString(const std::wstring& s);