FIX #1650: ".boot modules interact badly with the ghci debugger"
In fact hs-boot files had nothing to do with it: the problem was that GHCi would forget the breakpoint information for a module that had been reloaded but not recompiled. It's amazing that we never noticed this before. The ModBreaks were in the ModDetails, which was the wrong place. When we avoid recompiling a module, ModDetails is regenerated from ModIface by typecheckIface, and at that point it has no idea what the ModBreaks should be, so typecheckIface made it empty. The right place for the ModBreaks to go is with the Linkable, which is retained when compilation is avoided. So now I've placed the ModBreaks in with the CompiledByteCode, which also makes it clear that only byte-code modules have breakpoints. This fixes break022/break023