RFR(S): 8239072: subtype check macro node causes node budget to be exhausted

[Vladimir Ivanov]

> http://cr.openjdk.java.net/~roland/8239072/webrev.01/

Looks good.

Initially I thought that it would be beneficial to aggregate IGVN pass 
over multiple expansions, but now I think it's perfectly fine to 
initiate it after every node expansion.

Best regards,
Vladimir Ivanov