Add more 'step' tests to gdb.base/watchpoint.exp

The test gdb.base/watchpoint.exp has a proc named 'test_stepping'
which claims to "Test stepping and other mundane operations with
watchpoints enabled".  It sets a watchpoint on ival2, performs an
inferior function call (which is not at all mundane), and uses 'next',
'until', and, finally, does a 'step'.

However, that final 'step' command steps to (but not over/through) the
line at which the assignment to ival2 takes place.  At no time while
performing these operations is a watchpoint hit.

This commit adds a test to see what happens when stepping over/through
the assignment to ival2.  The watchpoint on ival2 should be triggered
during this step.  I've added another 'step' to make sure that the
correct statement is reached after performing the watchpoint-hitting
step.

After running the 'test_stepping' proc, gdb.base/watchpoint.exp does
a clean_restart before doing further tests, so nothing depends upon
'test_stepping' to stop at the particular statement at which it had
been stopping.

I've examined all tests which set watchpoints and step.  I haven't
been able to identify a(nother) test case which tests what happens
when stepping over/through a statement which triggers a watchpoint.
Therefore, adding these new 'step' tests is testing something which
hasn't being tested elsewhere.

Reviewed-By: John Baldwin <jhb@FreeBSD.org>

gdb/testsuite/gdb.base/watchpoint.exp

@@ -340,6 +340,15 @@ proc test_stepping {} {
 	}
 
 	gdb_test "step" "ival2 = count.*" "step to ival2 assignment"
+
+	# Check that the watchpoint is triggered during a step.
+	gdb_test "step" \
+		 "\[Ww\]atchpoint.*: ival2.*Old value = -1.*New value = 4.*ival3 = count; ival4 = count;" \
+		 "step over ival2 assignment"
+
+	# Step again and check that correct statement is reached after
+	# hitting a watchpoint during a step.
+	gdb_test "step" "marker2 \\(\\);.*" "step to marker2"
     }
 }