Include OSX 10.12 name and branding in wxGetOsDescription()

Starting with 10.12 OSX will be renamed to macOS. The name for version 10.12
is Sierra.

Closes https://github.com/wxWidgets/wxWidgets/pull/297

docs/changes.txt

@@ -114,6 +114,7 @@ wxOSX:
 - Turn off automatic quotes substitutions in wxTextCtrl (Xlord2).
 - Implement wxDataViewChoiceByIndexRenderer (wanup).
 - Fix unnecessary indentation in list-like wxDataViewCtrl (Andreas Falkenhahn).
+- Recognize macOS 10.12 Sierra in wxGetOsDescription() (Tobias Taschner).
 
 Unix:
 

src/osx/cocoa/utils_base.mm

@@ -109,7 +109,8 @@ wxString wxGetOsDescription()
     // Notice that neither the OS name itself nor the code names seem to be
     // ever translated, OS X itself uses the English words even for the
     // languages not using Roman alphabet.
-    wxString osBrand = "OS X";
+    // Starting with 10.12 the macOS branding is used
+    wxString osBrand = wxCheckOsVersion(10, 12) ? "macOS" : "OS X";
     wxString osName;
     if (majorVer == 10)
     {
@@ -132,6 +133,9 @@ wxString wxGetOsDescription()
             case 11:
                 osName = "El Capitan";
                 break;
+            case 12:
+                osName = "Sierra";
+                break;
         };
     }
 #else