Generated PC files may cause include shadowing

[antoniovazquezblanco]

For compat reasons, PC files generated by sigutils force to include second level directories via CFLAGS.

It would be best to avoid this but it breaks compilation of suscan and sigdigger. This means that this fix must be timed adecuatedly.

Refs: #53

[antoniovazquezblanco]

Having a deeper look at the issue, the current includes structure is:

include
    └───sigutils
        └───sigutils
            ├───specific
            └───util

A possible fix may be to reestructure to:

include
    └───sigutils
        ├───specific
        └───util

and simultaneously remove the conflicting include parameter.

To be studied...

[antoniovazquezblanco]

Partial fix in #55

Following steps require fixes in Suscan and Sigdigger. If includes are fixed in this dependent programs, the ofending PC lines can be removed afterwards.

[antoniovazquezblanco]

Improved include practices in:

BatchDrake/suscan#67
BatchDrake/SigDigger#206
BatchDrake/SuWidgets#20

This is another partial fix to the issue. After all the mentioned issues are tested and merged, finally, the ofending PC lines can be removed.

[antoniovazquezblanco]

All ofending imports have been fixed. Theoretically, level directory inclusion CFLAGS can be removed at the moment.

In order to prevent possible compilation errors with older versions of SigDigger and Suscan with newer Sigutil versions, it may be interesting to postpone this issue fix for a release.