`CONFIGATOR_MAX_LINE` is non-overridable and has a bad default

[3442]

configator.h reads:

#define CONFIGATOR_MAX_LINE 80

Just 80 bytes is pretty bad and not justified at all. This is currently blocking ly support in NixOS, since /nix/store path are usually long, specially when multiple store objects are involved. The default should be much larger at the very. More over, maybe we can require configator users to provide their own line buffer so as to prevent an arbitrary limit?