* df-problems.c (df_live_scratch): Convert to bitmap_head.
	(df_live_alloc): Initialize df_live_scratch when initializing
	problem_data.
	(df_live_transfer_function): Update uses of df_live_scratch.
	(df_live_free): Free problem_data; clear df_live_scratch before
	releasing the obstack.
	(df_md_free): Free problem data.

From-SVN: r160612