drop --with-systemdsleep and move logind detection to runtime

There is no need to bind the user to either systemd-logind or upower
at build time. People can switch between init systems or run logind
without systemd.
drop --with-systemdinhibit and move logind detection to runtime

There is no need to bind the user to either systemd-logind or upower
at build time. People can switch between init systems or run logind
without systemd.
gpm-prefs-core: fix can_shutdown when logind is in use
Add systemd Shutdown() API support to gpm-control.c
Fix gpm_prefs_init return values
Merge pull request #61 from lxnay/fix-github-master

Move logind / consolekit detection to runtime