added WXDLLIMPEXP_BASE for a couple of template classes having only inline functions as VC7 still needs them in DLL build if these classes are used as base classes or members of other DLL-exported classes (replaces first two parts of the patch 1779004)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@48681 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/string.h

@@ -2766,7 +2766,7 @@ private:
 #endif // !wxUSE_STL_BASED_WXSTRING
 
 template<typename T>
-class wxStringTypeBufferBase
+class WXDLLIMPEXP_BASE wxStringTypeBufferBase
 {
 public:
     typedef T CharType;
@@ -2784,7 +2784,7 @@ protected:
 };
 
 template<typename T>
-class wxStringTypeBufferLengthBase
+class WXDLLIMPEXP_BASE wxStringTypeBufferLengthBase
 {
 public:
     typedef T CharType;