checkpatch.pl: Check .cpp files

Enable checkpatch.pl to apply the same checks as C source files for
C++ files with .cpp extensions. It also adds some exceptions for C++
sources to suppress errors for:
  - <> used in C++ template arguments (e.g. template <class T>)
  - :: used to represent namespaces   (e.g. SomeClass::method())
  - : used in class declaration       (e.g. class T : public Super)
  - ~ used in destructor method name  (e.g. T::~T())
  - spacing around 'catch'            (e.g. catch (...))

Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama@hds.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
