Add test for use of "<block>::<variable>" syntax for locals in watch.

Add test for use of "<block>::<variable>" syntax for locals in watch.

First, fix a technical problem with the function recurser.  The test sets a
watch on local_x at a point where its value is technically undefined.  The
test is written assuming that the value is not initially 2, but nothing in the
C standard guarantees that.

Second, augment the existing test for variables in recursive calls to check an
equivalent expression that explicitly sets the scope of the local variable
being tracked.

2012-01-11  Paul Hilfinger  <hilfingr@adacore.com>

	* gdb.base/watchpoint.c (recurser): Initialize local_x.
	(main): Repeat recurser call.
	* gdb.base/watchpoint.exp: Check that 'watch recurser::local_x' is
	equivalent to 'local_x'.