This patch removes includes that are not used. The removals were found with
include-what-you-use which checks if any of the symbols from a header is
in use.
I'm assuming that it's fine if a _const_ or _pure_ function
calls assert. It is assumed that the assert won't trigger,
and even if it does, it can only trigger on the first call
with a given set of parameters, and we don't care if the
compiler moves the order of calls.
Because "export key=val" is not supported by systemd, an error is logged
where the invalid assignment is coming from.
Introduce strv_env_clean_log() to log invalid environment assignments,
where logging is possible and allowed.
parse_env_file_internal() is modified to allow WHITESPACE in keys, to
report the issues later on.
Now, actually check if the environment variable names and values used
are valid, before accepting them. With this in place are at some places
more rigid than POSIX, and less rigid at others. For example, this code
allows lower-case environment variables (which POSIX suggests not to
use), but it will not allow non-UTF8 variable values.
All in all this should be a good middle ground of what to allow and what
not to allow as environment variables.
(This also splits out all environment related calls into env-util.[ch])
