configure: include --enable-capabilities in help output

Include --enable-capabilities and --disable-capabilities in help output.

Author: davmac314

configure

@@ -197,8 +197,10 @@ Optional options:
   --shutdown-prefix=PREFIX          Name prefix for shutdown, poweroff, reboot, soft-reboot, halt programs []
   --enable-shutdown                 Build shutdown, poweroff, reboot, soft-reboot, halt programs [Enabled only on Linux systems]
   --disable-shutdown                Don't build shutdown, poweroff, reboot, soft-reboot, halt programs
-  --enable-cgroups                  Enable Cgroups support [Enabled only on Linux based systems]
+  --enable-cgroups                  Enable Cgroups support [Enabled only on Linux systems]
   --disable-cgroups                 Disable Cgroups support
+  --enable-capabilities             Enable capabilities support [Enabled on Linux if libcap available]
+  --disable-capabilities            Disable capabilities support
   --enable-utmpx                    Enable manipulating the utmp/utmpx database via the related POSIX functions [guessed]
   --disable-utmpx                   Disable manipulating the utmp/utmpx database via the related POSIX functions
   --enable-initgroups               Enable initialization of supplementary groups for run-as [Enabled]