* cse.c: Change encoding of quantity numbers to avoid undefined
	pointer arithmetic on qty_table.
	(REGNO_QTY_VALID_P): A quantity is now valid if it isn't negative.
	(get_cse_reg_info): Initialize reg_qty to a unique negative value.
	(new_basic_block): Assign "real" quantity numbers from zero.
	(delete_reg_equiv): Do nothing if quantity is invalid.  Reset the
	REG_QTY to its unique negative value.
	(merge_equiv_classes): Calculate need_rehash if quantity is valid.
	(cse_main): Don't include max_reg when determining max_qty.
	(cse_basic_block): Avoid subtracting a large offset from qty_table,
	which causes undefined C99 behaviour.  Only allocate needed memory.

Co-Authored-By: John David Anglin <dave.anglin@nrc-cnrc.gc.ca>

From-SVN: r89543