Update c++ file extensions supported

<Replicating what I've already said on the mailing list>

I understand why you needed this patch because I have a similar one in my changeset

But, quite frankly, I think this is nowhere near enough. The C++ world is a mess and far too heterogeneous to attempt to
satisfy everyone with one set of file name extensions. For example, in the project I have currently to work with, "*.C" means "C++" and
"*.cxx" means "autogenerated C++", the ".h"-files correspond to the ".C"-files and ".hpp"-files correspond to the ".cxx",
and there are chances that you dont wanna analyze the automatically generated stuff at all. And I dont doubt a second, that there
are code bases out there where the situation is exactly the opposite.

Therefore we should have a configuration option for this, IMO. And this list should serve as fallback if there's nothing configured.

What do you think?

I think cxx sonar should set a default file extension list. And this list should be updatable throw a property.
It will be next step.

Patch applied. Furthermore, as described in the comments, introduced a new property sonar.cxx.suffixes which can be used to configure the extensions to be used