Serialize built-ins on 'ant dist'

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
Introduce ForTestCompileBuiltIns

It's needed in ForTestCompileRuntime and in tests which compile Java sources.
In the latter case, javac should have Kotlin built-in classes in classpath to
be able to test usages of built-ins in Java code. Previously they just took
class files produced by IDEA from 'out/', but soon built-ins won't be compiled
by IDEA (and even if they would be, they're compiled by the bootstrap compiler
whereas stdlib in ForTestCompileRuntime is compiled by the working copy
compiler, which could cause all kinds of strange errors), so we need to compile
them manually
Compile built-ins with the new compiler in build.xml

Instead of nested "withKotlin" element in javac2 which launches
bootstrap-compiler, we launch K2JVMCompiler from the newly built compiler
directly
Unmark source roots in 'builtins' and 'runtime.jvm'

This is needed because until we have modules and dependencies implemented in
our IDEA plugin, the whole project always is analyzed to highlight any file in
the project. This resulted in weird errors in different modules in Kotlin
project because two declarations were found for each built-in class: the one in
kotlin-runtime.jar and the one (totally unrelated) in the 'builtins' module
Fix built-ins reference resolve tests

Built-in sources are contained now in two directories: compiled and
non-compiled (native). kotlin-plugin.jar has them both under 'jet/', but for
tests we manually specify where to look for the former, as it was for the
latter in LightClassUtil.java