Code review for LIKE ... INCLUDING INDEXES patch. Fix failure to propagate

 Code review for LIKE ... INCLUDING INDEXES patch.  Fix failure to propagate
 constraint status of copied indexes (bug #3774), as well as various other
 small bugs such as failure to pstrdup when needed.  Allow INCLUDING INDEXES
 indexes to be merged with identical declared indexes (perhaps not real useful,
 but the code is there and having it not apply to LIKE indexes seems pretty
 unorthogonal).  Avoid useless work in generateClonedIndexStmt().  Undo some
 poorly chosen API changes, and put a couple of routines in modules that seem
 to be better places for them.