busybox: applets as individual binaries

The individual binaries option of busybox allows for the applets
that would usually be symlinks to be built as individual applications
that link against a shared library.

This feature is needed for SELinux to allow the applications to run
under the correct SELinux context.

The patch being added allows the individual applications to be
installed and will be upstreamed to the busybox developers.

The initial work for this change was done by Thomas Petazzoni
<thomas.petazzoni@free-electrons.com>.

Signed-off-by: Clayton Shotwell <clayton.shotwell@rockwellcollins.com>
Signed-off-by: Matthew Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Niranjan Reddy <niranjan.reddy@rockwellcollins.com>
Signed-off-by: Bryce Ferguson <bryce.ferguson@rockwellcollins.com>
[Thomas:
 - add help text in Config.in option.
 - rename BUSYBOX_CONFIGURE_INDIVIDUAL_BINARIES to
   BUSYBOX_SET_INDIVIDUAL_BINARIES to be consistent with other
   variables.
 - call BUSYBOX_INSTALL_INDIVIDUAL_BINARIES in
   BUSYBOX_INSTALL_TARGET_CMDS, not in BUSYBOX_INSTALL_INIT_SYSV.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
[Arnout:
 - revert to the "optional file" approach in makedevs;
 - reword Config.in comment text to match our usual pattern;
 - abbreviate comment about how suid applets are found a little;
 - all applets are optional (each one may have been unselected from the
   busybox config).]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
[Thomas: remove /usr/share/udhcpc/default.script from BUSYBOX_PERMISSIONS.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>