A kbuild and kconfig maintainer change

For eight years, Masahiro Yamada has been the sole maintainer of the
kernel's build and configuration systems — two complex pieces of
infrastructure that many people interact with, but few truly understand.
Yamada has just stepped
down from that position. Maintenance of the build system will be taken
up by Nathan Chancellor and Nicolas Schier (in the 'odd fixes' capacity),
while the configuration system is now entirely unmaintained.

Thanks are due to Yamada for all that work, and to Chancellor and Schier
for stepping up. Hopefully a way will be found to better support these
important subsystems in the near future.