linux-libc-headers: create a libc-headers based on Wind River kernel

linux-libc-headers: create a libc-headers based on Wind River kernel

Put PREFERRED_PROVIDER_linux-libc-headers = "linux-libc-headers-wrs"
in your configuration, and this package will be used to generate a
set of kernel headers from the -standard branch of the Wind River kernel.

Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>