STYLE: Use regular expressions for Style namespace false positives.

itk.* are in the itk::tube namespace.

There are various .*\.cxx exceptions, but a .cxx file will have a .h
file anyway.

qSlicer.* and UI.h are Qt files without a namespace.

Change-Id: I1c51cb41102d2e15f99a865e25c3104bfa9b4320