Make SegmentList.has_blocks a property.
Make SegmentList.has_blocks a property.

This commit fixes GitLab issue 183
(https://github.com/angr/angr/issues/183).

angr/angr,chubbymaggie/angr,chubbymaggie/angr,tyb0807/angr,iamahuman/angr,schieb/angr,angr/angr,iamahuman/angr,f-prettyland/angr,f-prettyland/angr,tyb0807/angr,tyb0807/angr,axt/angr,angr/angr,f-prettyland/angr,axt/angr,chubbymaggie/angr,axt/angr,iamahuman/angr,schieb/angr,schieb/angr