* builtins.c (fold_builtin_cabs): Fold cabs(x+xi) into
	fabs(x)*sqrt(2).
	* fold-const.c (fold_binary): Fix comment typos.  Fold complex
	(x,0)-(0,y) into (x,-y).  Likewise (0,y)-(x,0) into (-x,y).

testsuite:
	* gcc.dg/builtins-54.c: Add more cases.

From-SVN: r121542