Move scheduler instrumentation hooks out of sched.h (where they seem like application interfaces) and into nuttx/sched.h where it is clare that these are OS internal interfaces.

MTD struct mtd_geometry_s:  Increase the size of blocksize again.  Yes, there are devices with block size greater than 64KB.

Build system: Add 'make oldconfig' target.  Use this option in tools/testbuild.sh.  Add --silent option to tools/refresh.sh so that it can be run in batch without human interaction

tools/testbuild.sh: kconfig-conf was silently failing because (1) it needs to execute from the top-level NuttX directory and (2) apps/Kconfig does not yet exist