Add click-buildtool compile-shortensyms.

This is better than putting && in a Linux kernel compile command,
apparently.
Fixincludes tweak for some Linux versions.
Linux compilation: Use debug_flags if it exists.

Which requires compiling a C file (conftest.c), since make mistakes
nonexistent.o for an asm file.

Centos/RHEL issues reported by Keith Schoenefeld.
CPUQueue: Too many CPUs is a runtime error, not a compile-time error.
Linuxmodule scheduler: Use newer CPU-getter interfaces.
Update configure from configure.in.
We are past Linux 2.6 now, update the message.
Linuxmodule install: "Install -C" is painful on CentOS, so replace it.

With a hand-written "installtree" addition to click-buildtool. Which
depends on md5sum existing, oh well.

Signed-off-by: Eddie Kohler <ekohler@gmail.com>
Update configure
Fix grammar
Merge branch 'master' of git://github.com/kohler/click