Patch to cccp.c to display omitted default include directories

[Nick Clifton]

Hi Jeff,

:   > 	* cccp.c (struct default_include): Add 'included' field.
:   > 	(main): Set 'included' field when a default include directory
:   > 	is added to the chain.  If -v is specified list all default
:   > 	include directories which do not get appended to the chain.

I have checked this patch in, so at least the basic code is there now.

: Can you do the same thing for cpplib?

I think Zack is on top of this.

: It might make sense to have this conditional on a warning flag (a
: generic one, or a specific one would be fine by me).

I was considering adding a new warning flag, not enabled by -Wall, to
control this feature, but it seemed that the -v switch was already
performing a very similar thing when it displayed the incldue paths
that were being used, so I just added my new feature to its output.

: It might be good improve the warning to note why those directories
: did not get added to the chain (because they didn't exist? any other
: reason they would not get added?)

I will have a look at this at some point, although for now I think
that humans are pretty good at figuring out why specific directories
were not chosen.

Cheers
	Nick