* fname for generic file paths
* tor_fname for paths relative to the top-level tor directory
* src_fname for paths relative to tor's src directory
With prefixes as required to disambiguate different paths of the same
type.
Part of 32962.
* distinguish between paths relative to the top-level tor directory,
and paths relative to tor's src directory
* canonicalise paths before using them
* check that the script is run from the top-level tor directory
* check that the file is being created in tor's src directory
Part of 32962.
Right now, this has been done at a high level by confparse.c, but it
makes more sense to lower it.
This API is radically un-typesafe as it stands; we'll be wrapping it
in a safer API as we do #30914 and lower the struct manipulation
code as well.
Closes ticket 30864.
