Move "equals" and "toString" extensions to stdlib

Since a lot of our tests assume that "equals" and "toString" are available and
it's not nice to require the full stdlib to be compiled before each such test,
we now compile a small subset of stdlib (consisting at the moment of a single
file, Core.kt) to be used only in tests
Rewrite JetPsiChecker test, add minimal runtime
Move FunctionImpl classes from package "jet" to "kotlin"
Move CollectionToArray from package "jet" to "kotlin"
Fix rangeTo between Float and Long

Float.rangeTo(Long) and Long.rangeTo(Float) now both return DoubleRange. Floats
can store a lot less than longs, so FloatRange is not acceptable. DoubleRange
seems the best we can do here
Fix VerifyError on rangeTo on primitive types
Delete jet.runtime.Ranges intrinsics

All these "rangeTo" methods were pretty small and could be generated just right
into "rangeTo" function calls
Include bootstrap runtime in kotlin-compiler.jar

This allows Kotlin compiler to be compatible only with the version of runtime
it was built against. This is currently done only on the first cycle of our
bootstrap process (the final released compiler is still shipped with a separate
runtime)
Move JVM Intrinsics class to package "kotlin.internal"

Delete unused intrinsics, reformat code, rename some declarations for better
readability
Move and rename jet.runtime.SharedVar -> kotlin.internal.Ref
Move jet.runtime.ArrayIterator to package "kotlin.internal"
Delete unused DefaultJetObject
Move jet.JetObject -> kotlin.internal.KObject

Don't use JetObject as a marker class in KotlinRuntimeLibraryUtil anymore,
since there are other classes for this purpose (KotlinPackage, Unit)
Remove ClassLoaderIsolationUtil

Minimize usages of jet.* in Java code: this will help in migration of jet.* to
package kotlin. Since tests will work with fq names instead of Class<?>
instances from now on, ClassLoaderIsolationUtil is useless now (except for one
unrelated method, which was moved to CodegenTestUtil)
Move jet.Kotlin* annotations to package "kotlin.internal"

Also rename poorly named KotlinPackageFragment -> KotlinPackagePart