main: don't free fds array twice
local: fix memory leak when putting together locale settings

Also, we need to use proper strv_env_xyz() calls when putting together
the environment array, since otherwise settings won't be properly
overriden.

And let's get rid of strv_appendf(), is overkill and there was only one
user.
hashmap: size hashmap bucket array dynamically

Instead of fixing the hashmap bucket array to 127 entries dynamically
size it, starting with a smaller one of 31. As soon as a fill level of
75% is reached, quadruple the size, and so on.

This should siginficantly optimize the lookup time in large tables
(from O(n) back to O(1)), and save memory on smaller tables (which most
are).
Update TODO
Revert "build-sys: link libsystemd-login with libsystemd-label.la"

Systemd-logind does not pull in cg_create(), if we unconditionally link
this, all users of systemd-logind qill need the label stuff and therefore
link against selinux.

It is probably a build-system issue, or something that need to be sorted
out in a differnt way than linking not needed libs.

This reverts commit ceadabb102b05b237bfab11e1f742975ee4daeb1.