dump reasons why graphite failed to detect a scop

dump reasons why graphite failed to detect a scop

When trying to analyze why Graphite does not handle a loop nest, it is easy to
look in the dumps of -fdump-tree-graphite-all to guess what has to be changed to
catch the loop.  This patch makes the dumps a bit more verbose and useful.

	* graphite-scop-detection.c: Include gimple-pretty-print.h.
	(stmt_simple_for_scop_p): Print when a stmt is not handled in Graphite.
	(scopdet_basic_block_info): Print when a loop or bb cannot be
	represented in Graphite.

From-SVN: r226213