rhbz#1559633: Treat EPERM same as EACCES when opening files

For example, Linux open(2) with O_RDWR fails with EPERM if the file is flagged
as FS_IMMUTABLE_FL.  (And there is an #ifdef IOS "Horrible hack" block in
openFilePath in sal/osl/unx/file.cxx that is apparently a workaround for a
similar scenario where open returns EPERM instead of EACCES on iOS, and which
can probably be removed again after this commit.)

Change-Id: I00cbd28d4b83b223920776998e9245b6261bb748
Reviewed-on: https://gerrit.libreoffice.org/51788Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

ucb/source/ucp/file/filglob.cxx

@@ -310,6 +310,7 @@ namespace fileaccess {
                 case FileBase::E_ROFS:
                     // #i4735# handle ROFS transparently as ACCESS_DENIED
                 case FileBase::E_ACCES:
+                case FileBase::E_PERM:
                     // permission denied<P>
                     ioErrorCode = IOErrorCode_ACCESS_DENIED;
                     break;