gcc: Sane defaults when optimization.* file doesn't exist

This also allow us to fiddle less with our iso build tools
everytime the compiler etc is bumped.

Yes, we default to i686 or x86-64 for the CPU, since that's what
we use iwhen building the ISO.
binutils: Sane optimization defaults for the menu
ccache: enable ccache default
optimization-plugins: moved the defaults variables

Moved the defaults for the menus to conform with the rest of the code
plugins: added functions setting the defaults for gcc and binutils
Merge branch 'optimization_defaults'