Clean up IsSecureURL

...to not use WildCard (in case a trusted location URI already contains an
unescaped "*"), be specific about matching only past a final "/", and rename to
isSecureMacroUri for clarification.

The check with an INET_PROT_NOT_VALID default INetURLObject in
SfxApplication::OpenDocExec_Impl ("we have to check the referer before
executing") had efficiently been dead since its inception in
14237ac4bf497decdde8b742acea23780833ba12 "#90880#: security checks corrected,"
as INET_PROT_NOT_VALID is considered secure regardless of referer anyway.

Change-Id: I03bca5e6dac89bb2aac52909aff273ea640228d8