Use type aliases FilePath, FilePaths...

... for wxString and wxArrayStringEx, holding file paths (absolute or relative,
directory or plain file); to be replaced later with different types

(not yet using std::vector, becase of some uses of wxArrayString::Index with
two arguments)

include/audacity/EffectInterface.h

@@ -253,8 +253,8 @@ public:
    virtual ~EffectManagerInterface() {};
 
    virtual void FindFilesInPathList(const wxString & pattern,
-                                    const wxArrayString & pathList,
-                                    wxArrayString & files,
+                                    const FilePaths & pathList,
+                                    FilePaths & files,
                                     int searchFlags) = 0;
 };
 

include/audacity/ModuleInterface.h

@@ -89,7 +89,7 @@ public:
    // Returns empty, or else, where to copy a plug-in file or bundle.
    // Drag-and-drop is supported only if GetFileExtensions() returns nonempty and
    // this function returns nonempty.
-   virtual wxString InstallPath() = 0;
+   virtual FilePath InstallPath() = 0;
 
    // Modules providing a single or static set of plugins may use
    // AutoRegisterPlugins() to register those plugins.

include/audacity/PluginInterface.h

@@ -68,8 +68,8 @@ public:
    virtual const PluginID & RegisterPlugin(ModuleInterface *provider, ImporterInterface *importer) = 0;
 
    virtual void FindFilesInPathList(const wxString & pattern,
-                                    const wxArrayString & pathList,
-                                    wxArrayString & files,
+                                    const FilePaths & pathList,
+                                    FilePaths & files,
                                     bool directories = false) = 0;
 
    virtual bool GetSharedConfigSubgroups(const PluginID & ID, const RegistryPath & group, RegistryPaths & subgroups) = 0;

include/audacity/Types.h

@@ -73,6 +73,9 @@ class wxArrayStringEx;
 using FileExtension = wxString;
 using FileExtensions = wxArrayStringEx;
 
+using FilePath = wxString;
+using FilePaths = wxArrayStringEx;
+
 // ----------------------------------------------------------------------------
 // A native 64-bit integer...used when referring to any number of samples
 // ----------------------------------------------------------------------------