Replace a non-working icecc class with a rewritten one. It's cleaned up,
most things are handled now in shell scripts, as it's possible that
toolchains won't exist at the time of parsing/python substitution.
Packages which empty PARALLEL_MAKE are ignored now, as not to break
them.
Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
