kconfig: allow stdin/stdout redirection

Allow stdin/stdout redirection for the CLI conf (not mconf).
This allows to recall a sample and automatically apply the defaults
to new configuration option, with something like the following:
yes "" |ct-ng "sample_name"

docs: add a tutorial on how to build a toolchain on Mac OS-X

Add a step-bystep tutorial to build a cross-toolchain on Mac OS-X.

companion libs: add latest CLooG/PPL versions

Add the latest 0.15.{4,5,6,7} CLoog/PPL.

samples: show the PPL, GLoog/ppl and MPC versions

When displaying a sample, do show the PPL, CLoog/ppl and MPC versions

samples: fix displaying selected tools

Do display selected tools / debug facilities when displaying a sample.

samples: replace usage of echo with printf

Using printf instead of echo allows easier and better formatting.

tools wrapper: fix building

Remove the build tools only after the wrapper is built.
Use the corect C compiler to build the tools wrapper.
Use the correct log level.

crosstool.sh.in: better mesage when creating script-overrides

log functions: fix CT_DoLog and CT_DoExecLog

$@ and $* are different when in double quotes; use $* to print the message.

tools wrapper: move choice selection to a more appropriate place

Move the tools wrapper choice selection down to the companion libraries
sub-menu, to avoid the user going back and forth in the menu.