toolchain/crosstool-NG: bundle one CT-NG config file for each libc familly

Currently, the bundled CT-NG config file has no C library configured.
It is quite complex to add and/or munge options in this case.

Now, with one config file per libc familly, it becomes easier.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>