Major changes. Now we only compactify individual type planes if it is in

Major changes.  Now we only compactify individual type planes if it is in
fact "profitable" to do so.  This makes compactification "free" for small
programs (ie, it is completely disabled) and even helps large programs by
not having to encode pointless compactification planes.

On 176.gcc, this saves 50K from the bytecode file, which is, alas only
a couple percent.

This concludes my head bashing against the bytecode format, at least for
now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10922 91177308-0d34-0410-b5e6-96231b3b80d8