ckmake: address directory max depth

It seems new versions of python make the os walk recurse more
than we used to before, our ckmake implementation was picking up
more kernels targets than obviously we want to build then. Fix
this by replacing the os.walk() with a simple os.listdir()
which just keeps us at the top level directory of lib/modules.

While at it, this adds the --develdebug option which lets you
debug the the directory naming it will use for display and what
directories it will traverse without actually compiling anything
and without using ncurses. For instance to debug or ckmake without
compilation you can use:

$ ckmake --allyesconfig --develdebug
Paths for kernels:
3.4.103-0304103-generic
3.9.11-030911-generic
3.2.62-030262-generic
3.16.2-031602-generic
3.11.10-031110-generic
3.8.13-030813-generic
3.5.7-03050712-generic
3.0.101-0300101-generic
3.15.10-031510-generic
3.6.11-030611-generic
3.13.11-031311-generic
3.1.10-030110-generic
3.10.54-031054-generic
3.3.8-030308-generic
3.7.10-030710-generic
3.14.18-031418-generic
3.17.0-031700rc3-generic
3.12.27-031227-generic
IDX VERSION	DIRECTORY
1   3.0.101	/home/mcgrof/ksrc-backports/lib/modules/3.0.101-0300101-generic
2   3.1.10	/home/mcgrof/ksrc-backports/lib/modules/3.1.10-030110-generic
3   3.2.62	/home/mcgrof/ksrc-backports/lib/modules/3.2.62-030262-generic
4   3.3.8	/home/mcgrof/ksrc-backports/lib/modules/3.3.8-030308-generic
5   3.4.103	/home/mcgrof/ksrc-backports/lib/modules/3.4.103-0304103-generic
6   3.5.7	/home/mcgrof/ksrc-backports/lib/modules/3.5.7-03050712-generic
7   3.6.11	/home/mcgrof/ksrc-backports/lib/modules/3.6.11-030611-generic
8   3.7.10	/home/mcgrof/ksrc-backports/lib/modules/3.7.10-030710-generic
9   3.8.13	/home/mcgrof/ksrc-backports/lib/modules/3.8.13-030813-generic
10  3.9.11	/home/mcgrof/ksrc-backports/lib/modules/3.9.11-030911-generic
11  3.10.54	/home/mcgrof/ksrc-backports/lib/modules/3.10.54-031054-generic
12  3.11.10	/home/mcgrof/ksrc-backports/lib/modules/3.11.10-031110-generic
13  3.12.27	/home/mcgrof/ksrc-backports/lib/modules/3.12.27-031227-generic
14  3.13.11	/home/mcgrof/ksrc-backports/lib/modules/3.13.11-031311-generic
15  3.14.18	/home/mcgrof/ksrc-backports/lib/modules/3.14.18-031418-generic
16  3.15.10	/home/mcgrof/ksrc-backports/lib/modules/3.15.10-031510-generic
17  3.16.2	/home/mcgrof/ksrc-backports/lib/modules/3.16.2-031602-generic
18  3.17-rc3 	/home/mcgrof/ksrc-backports/lib/modules/3.17.0-031700rc3-generic

Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>