[flang] Catch attempts to initialize allocatable components with DATA statement

[klausler]

Summary

Nice try, but no, you can't initialize an instance of a derived type using a
structure constructor that has a component corresponding to an allocatable
component.

[PeteSteinfeld]

All builds and tests correctly and looks good.

flang/lib/Evaluate/initial-image.cpp

             return SizeMismatch;
           } else if (IsPointer(component)) {
             AddPointer(offset + component.offset(), indExpr.value());
+          } else if (IsAllocatable(component) || IsAutomatic(component)) {
+            return NotAConstant;
           } else {
             Result added{Add(offset + component.offset(), component.size(),
                 indExpr.value(), context)};

flang/test/Semantics/data01.f90

   integer, parameter :: repeat = -1
   integer :: myAge = 2
   type(person) associated
+  type hasAlloc
+    integer, allocatable :: a(:)
+  end type
 end
 
 subroutine CheckRepeat

   data y / a(i) /
   !ERROR: DATA statement value 'b(1_8)' for 'z' is not a constant
   data z / b(1) /
+  type(hasAlloc) ha
+  !ERROR: DATA statement value 'hasalloc(a=0_4)' for 'ha' is not a constant
+  data ha / hasAlloc(0) /
 end