gdb/testsuite: Run test with software and hardware watchpoints

gdb/testsuite: Run test with software and hardware watchpoints

Expand the gdb.base/watchpoint-reuse-slot.exp test to be run twice,
once with hardware watchpoints disabled (this is new) and then with
hardware watchpoints enabled (the old way).

Running with hardware watchpoints enabled is skipped if the board file
says that hardware watchpoints are not supported on this target.

gdb/testsuite/ChangeLog:

	* gdb.base/watchpoint-reuse-slot.exp: Test with hardware
	watchpoints enabled and disabled.