Fix Ada "ptype" bug with array types

Fix Ada "ptype" bug with array types

Using ptype on an array type in Ada can sometimes show an incorrect
high bound.  This happens because ada_evaluate_subexp will create an
array with an incorrect upper bound in the EVAL_AVOID_SIDE_EFFECTS
case.

This patch fixes the problem by arranging to always create such an
array with valid bounds.

Tested on x86-64 Fedora 29.

gdb/ChangeLog
2019-03-18  Tom Tromey  <tromey@adacore.com>

	* ada-lang.c (empty_array): Add "high" parameter.
	(ada_evaluate_subexp): Update.

gdb/testsuite/ChangeLog
2019-03-18  Joel Brobecker  <brobecker@adacore.com>
	    Tom Tromey  <tromey@adacore.com>

	* gdb.ada/ptype_array/pck.adb: New file.
	* gdb.ada/ptype_array/pck.ads: New file.
	* gdb.ada/ptype_array/foo.adb: New file.
	* gdb.ada/ptype_array.exp: New file.