ipa-cp: Make dumping of bit masks representing -1 nicer

Dumps of the lattices representing bit-values and of propagation
results of bit-values can print a really long hexadecimal value when
the bit-value represents -1 (all bits set).  This patch simply detect
that situation and prints the string "-1" in that case, making the
dumps somewhat nicer.

gcc/ChangeLog:

2025-01-03  Martin Jambor  <mjambor@suse.cz>

	* ipa-cp.cc (ipcp_print_widest_int): New function.
	(ipcp_store_vr_results): Use it.
	(ipcp_bits_lattice::print): Likewise.  Fix formatting.