#23 Make RefVerifier not find inherited constructors

[Don Schwarz]

RefVerifier.MethodVerifier currently walks up the class hierarchy looking for methods defined on the target class and any superclasses. However, this is not valid for constructors. Constructors are never inherited.

The practical result of this is that when trying to verify a missing constructor, for example IOException(String, Throwable) in Java 1.5, RefVerifier will see IOException(String, Throwable) and assume that these uses are valid.

[Don Schwarz]

Patch against trunk @ v419