kconfiglib: node: add 'loc' attribute

Replace 'filename' and 'linenr' usages with a single 'loc' attribute,
which is a (filename, linenr) tuple. This simplifies code dealing with
locations, and makes it explicitly constant. The original attributes are
now provided via properties for compatibility.

Signed-off-by: Luca Burelli <l.burelli@arduino.cc>
1 file changed