COMP: Unused Clone and CreateAnother warnings

The intel compiler recognizes that the Clone and CreateAnother can never
be used in this isolated compilation unit.  The itkSimpleNew
provides only what is needed.

Change-Id: I83cb0c29e938488bbea7a37c85bb5ac80d298309
BUG: Bug fixed in remote MGHImageIO repo, update git tag

This version also disallows the bare .gz extension for MGH
Image files.  The rationale for this is that it collides
dangerously with the NIfTI reader, specifically and
compressed files in general.  This means that MGHImageIO
will reject files it formerly accepted, but this is OK for
the following reasons:

1. It is unlikely that users regularly encounter MGH files with
just the '.gz' extension.

2. The primary producer and consumer of these files,
FreeSurfer, always uses by default one of the less ambiguous
file extensions.

3. If the user regularly encounters such files, they have
choices: they can use SetImageIO to force using the MGH
reader, or they can rename the files to a less ambiguous
file extension.

4. Allowing the option of '.gz' requires sufficient knowledge
of the user/developer to select that option, that one can
fairly assume the user/developer is knowledgeable enough to
cope with any issues arising from that option being
unavailable.

Change-Id: I59d792f4b1efa45a7bf86368d3f841cc9de96ef3
Merge topic 'FixMGHImageIOCanReadFile'

fb5eba8 BUG: Bug fixed in remote MGHImageIO repo, update git tag
Merge topic 'RemoveFalseSharingPatch1'

fb01c31 COMP: Unused Clone and CreateAnother warnings