Fixed -Wmissing-variable-declarations warnings in headers

Fixed by adding 'const' to several items.

As this changes headers, it might have an impact on
clients, but I don't think so...

Change-Id: Ib975e219e6e30e83ec2fc25feeae389b4f10507f
Fixed -Wmissing-variable-declarations warnings in .cxx

Fixed by adding 'static' and/or 'const' to several
variables that had neither.

Removed one obsolete comment too.

Change-Id: I8775c9a1fa8d9cc75b28619216bbe7f901117a0f
Merge topic 'Wmissing-variable-declarations' into master

648903ed Fixed -Wmissing-variable-declarations warnings in .cxx
7f8ca8e8 Fixed -Wmissing-variable-declarations warnings in headers