Further improvements to lib/krb5/n-fold.c:

	o  implement add1() using 32 bit ints, this makes _krb5_n_fold()
	   about 5% faster on an amd64 platform.  64 bit ints yield a
	   further improvement but we would need to test the platform
	   to see if they are natively supported.  This should yield
	   better performance improvements on big endian machines as
	   we have to byte swap on little endian boxen.

	o  fix two cases where a malloc(3)d pointer may be dereferenced
	   before we test that it is not NULL.