Deprecate network functions no longer used in neither in chrome nor entd.

This will fix the linux chromium os clang build, Value will be completely
gone from header files. Value is still in deprecated code in
chromeos_network.cc but will be removed in the near future.

Note that code still used in entd is preseved.

BUG=chromium-os:20578
TEST=gmerge libcros, entd, chrome

Change-Id: Iedfdb37bd0bbbd421c2a411c890fc69ea5c290bd
Reviewed-on: http://gerrit.chromium.org/gerrit/7929
Tested-by: Satoru Takabayashi <satorux@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>