Name the parameters of wxGetOsVersion consistently

Use verMaj and verMin like almost everywhere instead of majorVsn and
minorVsn in a couple of places.

include/wx/utils.h

@@ -140,8 +140,8 @@ WXDLLIMPEXP_CORE wxVersionInfo wxGetLibraryVersionInfo();
 WXDLLIMPEXP_BASE wxString wxGetOsDescription();
 
 // Get OS version
-WXDLLIMPEXP_BASE wxOperatingSystemId wxGetOsVersion(int *majorVsn = NULL,
-                                                    int *minorVsn = NULL);
+WXDLLIMPEXP_BASE wxOperatingSystemId wxGetOsVersion(int *verMaj = NULL,
+                                                    int *verMin = NULL);
 
 // Check is OS version is at least the specified major and minor version
 WXDLLIMPEXP_BASE bool wxCheckOsVersion(int majorVsn, int minorVsn = 0);