Introduce -IgnoreJDKClasses option for ignoring JDK classes and treat (legacy) -IgnoreJDKClass [jdkclass] option the same as -IgnoreJDKClasses

[scottmarlow]

If -IgnoreJDKClasses is specified, JDK classes will be ignored when testing/checking signatures.

With this change, we will also treat the following options the same as -IgnoreJDKClasses:

• IgnoreJDKClass javax.blah
• IgnoreJDKClass

Migration note: Change from -IgnoreJDKClass (or -IgnoreJDKClass className sequences) to only specify -IgnoreJDKClasses.

[scottmarlow]

I'm thinking that we will release a new sigtest release that ignores the IgnoreJDKClass (whether java class names are specified after or or not). Will see if that is possible.

[jamezp]

FWIW I don't think we should remove or ignore the -IgnoreJDKClass, we just re-introduce the old behavior removed in #30. The same approach for #30 could be used, but instead of using -IgnoreJDKClass we should use -IgnoreJDKClasses.