[libvirt] Use gnulib's c-ctype.h; prohibit use of <ctype.h>

[Jim Meyering]

Daniel Veillard <veillard at redhat.com> wrote:
...
>> The authoritative source for the license is specified in
>> the module-definition file, gnulib/modules/c-ctype.  It is LGPLv2+.
>
>   Looks quite confusing. The .h file says this module is under Licence X
> and somewhere a text file says it's under a different Licence Y. My instinctive
> reaction (and I guess i'm not the only one) is to assume the licencing
> information in the source would be the one binding from a legal POV,
> but IANAL, so all i can say is that it looks weird.
>
>> Besides, our invocation of gnulib-tool (in bootstrap) requires that
>> any module be compatible with LGPLv2+ via its --lgpl=2 option,
>> so this is checked automatically.  You may rest assured that
>> any module I propose for addition has the right copyright.
>> In addition, when gnulib-tool copies the files into gnulib, it
>> rewrites the license to be what we require:
>
>   Okay, i assume there is no problem, changing licences when copying
> exceeds my limited understanding, but there is certainly a good and
> legally okay reason for that, but I'm fine to stay ignorant as long
> as you tell me it's okay :-)

Yes, it's confusing, and we'd like it to be fixed.
It will be, eventually.