* gdb.mi/var-cmd.c: Give long_array in _struct_decl 12 elements.

* gdb.mi/var-cmd.c: Give long_array in _struct_decl 12 elements.
(do_children_tests): Assign values to the extra elements.

* gdb.mi/mi-var-child.exp: Adapt tests for extra elements and use
them for tests for "-var-update --no-values" and
"-var-update --all-values".
Add test for "-var-list-children --simple-values".

* gdb.mi/basics.c (callee4): Add integer array D[3]...

* gdb.mi/mi-stack.exp (test_stack_locals_listing): ...to test
"-stack-list-locals --simple-values"  Improve doc strings and
comments.