Fix compile1.bug6720 already defined error
Merge pull request #2720 from ibuclaw/compile1

Fix compile1.bug6720 already defined error
Implement qualified postblit (try 1)

Add `Expression::isUniqData()`
Implement qualified postblit (try 2 - buildFieldPostBlit)
Add target type to callCpCtor
+fix TypeStruct::implicitConvTo
++callCpCtor (not tested)
Implement qualified postblit (try 3 - support TypeInfo)
+typeinfo
+typeinfo 2
+stash
+stash 2 (CatAssignExp)
+typeinfo 3 (CatAssignExp)
+typeinfo 4 (AssignExp array.length = n;)
+typeinfo 5 (CatExp + issues)
-typeinfo
(stash) for runnable/sdtor.d