gdb/testuite/

	gdb/testuite/
	* gdb.trace/unavailable.cc (a, b, c): New globals.
	(main): Set and clear them.
	* gdb.trace/unavailable.exp (gdb_collect_globals_test): Collect
	`a' and `c', and check that `b' isn't collected, although `a' and
	`c' are.

	gdb/
	* tracepoint.c (memrange_sortmerge): Don't merge ranges that are
	almost but not quite adjacent.