reduce sparseset memory requirement

reduce sparseset memory requirement

Currently we use HOST_WIDEST_FAST_INT for the sparseset element
type which maps to a 64bit type on 64bit hosts.  That's excessive
for the only current sparseset users which are LRA and IRA and
which store register numbers in it which are unsigned int.  The
following changes the sparseset element type to unsigned int.

2021-02-09  Richard Biener  <rguenther@suse.de>

	* sparseset.h (SPARSESET_ELT_BITS): Remove.
	(SPARSESET_ELT_TYPE): Use unsigned int.
	* fwprop.c: Do not include sparseset.h.