Add option to retain #include directives in preprocessor

[seladb]

Please let me know if you're open to this change...

In the existing behavior - the preprocessor will remove #include headers that it can find in the current directory. For example, if these are the files in my folder:

|- t1.h
|- t2.h

Content of t1.h:

// t1.h

#include "t2.h

Content of t2.h:

// t2.h

...

When I run the preprocessor for t1.h, I won't see any includes:

{
    "includes": []
}

With this change I can see the include:

  "includes": [
    {
      "filename": "\"t2.h\""
    }
  ]

[virtuald]

I don't want this to be the default behavior. Add it as an option to make_pcpp_preprocessor instead?

[seladb]

I don't want this to be the default behavior. Add it as an option to make_pcpp_preprocessor instead?

Added here: 9fe4713
I'm not sure about the option name, please feel free to suggest another name...

Are you open to also expose it as an opition in dumpmain()? If yes, what should be the option name?

[virtuald]

I don't really think it makes sense to expose it in dumpmain, it already doesn't support all options and isn't really intended to be used directly, it's merely a tool to help you visualize the output when parsing something. As the documentation says "Anything more than that and you should use the python API".