[PATCH] Fix middle-end/15618, bool_var != 0 (== 1) -> bool_var

[Andrew Pinski <pinskia at physics dot uc dot edu>]

Right now we don't optimize if a bool variable is compared not equal
to zero or equal to one.  This implements that folding of those two
and treats BOOLEAN_TYPE like INTEGER_TYPE in fold_widened_comparison
so we get the folding of "(int)bool_var != 0" into "bool_var != 0".

OK? Bootstrapped and tested on powerpc-darwin7.8 without any 
regressions.

Thanks,
Andrew Pinski

ChangeLog:

	* fold-const.c (fold_widened_comparison): Treat BOOLEAN_TYPE
	the same as INTEGER_TYPE.
	(fold_binary): Fold "bool_var != 0" to bool_var.
	Fold "bool_var == 1" to bool_var.

testsuite/ChangeLog:

	* gcc.dg/tree-ssa/bool-[1-9].c: New tests.

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