Revert "Automatically mark classes with pure virtual functions as /Abstract/."

Authored by skelly on Feb 5 2017, 10:45 PM.

Description

Revert "Automatically mark classes with pure virtual functions as /Abstract/."

With some combination of PyQt/compiler this breaks the build of
kcoreaddons.

This reverts commit 2e20aeab6e86670a66ff99a7b79120c4004b4d22.