Compiler Optimisations

Wile the very historic versions of T2, before about the year 2000, the user could set CFLAGS (and others) in his shell before starting the build, and this resulted in unexpected behavior since it influenced with the optimizations chosen in ./scripts/Config.

These variables are cleared now in ./scripts/parse-config before building the packages. The configuration are chosen in the ./scripts/config and injected using the gcc wrapper. It's possible to add additional options in the Config or on a per-package or target basis.