Call ada_ensure_varsize_limit in indirection

Call ada_ensure_varsize_limit in indirection

Internal testing revealed yet another Ada regression from the
expression rewrite.  In this case, indirection did not use the Ada
varsize limit.  The old code relied on the expression resolution
process to evaluate this subexpression with EVAL_AVOID_SIDE_EFFECTS in
order to get this error.  However, this isn't always done in the new
approach; so this patch introduces another call to
ada_ensure_varsize_limit in the appropriate spot.

As with the earlier patches, this path was not tested in-tree, so this
patch also updates a test.

gdb/ChangeLog
2021-03-15  Tom Tromey  <tromey@adacore.com>

	* ada-lang.c (ada_unop_ind_operation::evaluate): Call
	ada_ensure_varsize_limit.

gdb/testsuite/ChangeLog
2021-03-15  Tom Tromey  <tromey@adacore.com>

	* gdb.ada/varsize_limit.exp: Add new test.
	* gdb.ada/varsize_limit/vsizelim.adb: Update.