Make it serialize data for all packages found in sources and not only
KotlinBuiltIns.FQ_NAME, i.e. "jet". This is required to migrate built-ins from
package "jet" to "kotlin"
Don't store binary data in the repository anymore. From now on any test on the
compiler requires that 'ant dist' was executed at least once since the last
update of the built-ins
BuiltInsSerializer will be distributed with Kotlin compiler from now on. This
will allow to serialize binary data of built-ins on 'ant dist', as opposed to
storing all *.kotlin_class files in the repository: ant dist will just invoke
this serializer from bootstrap-compiler.jar