remove dll export declaration from wxCStrData now that all its methods are inline (fixes mingw32 warning in DLL build)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@60184 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/string.h

@@ -209,7 +209,7 @@ inline int Stricmp(const char *psz1, const char *psz2)
 
 // Lightweight object returned by wxString::c_str() and implicitly convertible
 // to either const char* or const wchar_t*.
-class WXDLLIMPEXP_BASE wxCStrData
+class wxCStrData
 {
 private:
     // Ctors; for internal use by wxString and wxCStrData only