udev-cache related changes

This is v2 of the changes submitted by Ben Shelton on August 4. I've reworked the patches quite a bit, larger changes include:

- All non-udev-cache-related patches have been omitted. I'll submit those separately.
- Use find to build tar filelist. This eliminates the need for GNU- and busybox-specific tar options.
- No new settings have been added to udev-cache.default in order to preserve compatibility with older overrides of udev-cache.default. Note, this means a lot of new settings are duplicated between initscripts.
- System config is now generated immediately before the tarball is generated, and is manipulated at the file level instead of the shell variable level.
- Internal/corporate commit message fields stripped.
- Spurious whitespace changes should all be fixed.

There is one requested fix I'm pushing back on: Copying both $CMP_FILE_LIST and /dev to tmpfs in a single operation to minimize race conditions. For a variety of reasons, I abandoned trying to make this work in a single command. Instead it's done in two: grabbing the system configuration (i.e reading /proc files and udev rules) is done first, then /dev is archived as an uncompressed tarball. Notably, using tar instead of cp means that I can use find -xdev and find -type to eliminate a lot of other complexity. I think this approach will wind up being faster than the straight-up copy approach, although I have not made any attempt to confirm that.

The following changes since commit 47d1fc9f5c38f3d092937c47bd4c2f45adaa7fe6:

qemu: fix Darwin cross-compilation (2014-08-18 20:43:24 +0100)

are available in the git repository at:

git://github.com/rtollert/openembedded-core dev/rtollert/udev-cache-7
https://github.com/rtollert/openembedded-core/tree/dev/rtollert/udev-cache-7

Richard Tollerton (12):
udev-cache: Update cache tarball atomically
udev-cache: Compress the cache
udev-cache: choose a more descriptive cache filename
busybox: enable tar -m
udev-cache: strip timestamps on extract
udev-cache: omit sockets and filesystems mounted under /dev
udev-cache: Don't ignore error messages from cache extract
udev-cache: parametrize sysconf file paths
udev-cache: get system config immediately before cache
udev-cache: invalidate on rules.d changes
udev-cache: Update cache asynchronously
udev-cache: refactor; improve verbosity and error handling

 meta/recipes-core/busybox/busybox/defconfig    |  2 +-
 meta/recipes-core/udev/udev/init               | 53 ++++++++++++--------------
 meta/recipes-core/udev/udev/udev-cache         | 42 ++++++++++++++++++--
 meta/recipes-core/udev/udev/udev-cache.default |  2 +-
 4 files changed, 64 insertions(+), 35 deletions(-)

2.0.4