Fixed problem converting assembly attributes in the IKVM loader.

If we had

Assembly1:

    public class MyAttribute {}

Assembly2:

    [assembly: MyAttribute]

and we then tried to load Assembly2 with the IKVM loader, the loader would think that the attribute MyAttribute is defined in Assembly2 insteadof Assembly1. This would later cause the resolver to fail to resolve the attribute.
OptionalParameterMismatchIssue: Added support for null default values (which previously caused null reference exceptions).
OptionalParameterValueMismatchTests: Added new test demonstrating null default values.
Merge pull request #247 from erik-kallen/ikvm-assembly-attributes-fix

Fixed problem converting assembly attributes in the IKVM loader.
Merge pull request #246 from mono-soc-2013/luiscubal-optional-name-mismatch

Optional value mismatch
Fixed some formatting issues.
Synchronized 'OptionalParameterHierarchyMismatchIssue'.
Fixed possible exception.
Synced 'FunctionNeverReturnsIssue'.
Synced 'BitwiseOperationOnNonFlagsEnumIssue'.
Synced 'EnumUnderlyingTypeIsIntIssue'.
Merge branch 'master' of git://github.com/icsharpcode/NRefactory into luiscubal-optional-name-mismatch
OptionalParameterHierarchyMismatchIssue: Added support for null default values (which were apparently lost in a merge operation).
Added support for indexers in OptionalParameterHierarchyMismatchIssue