scripts: add "FILE" and "CFG" debug levels.

I ran into some minor difficulties looking through the build log for a
particular file: I wasn't interested in seeing it unpacked, but only
when it is built or installed. Adding these two levels allows me to
differentiate between those cases.

[Yann E. MORIN: Those are blind log levels, and are used only to search
in the build-log afterward.]

Signed-off-by: Anthony Foiani <anthony.foiani@gmail.com>

 # Compute Alpha-specific values

 CT_DoArchTupleValues () {

     # The architecture part of the tuple:

     CT_TARGET_ARCH="${CT_ARCH}${CT_ARCH_ALPHA_VARIANT}"

 }